Android build warnings about Java with latest Gradle: `source value 8 is obsolete`/`target value 8 is obsolete`

# Context

**My main question**: is [this comment](https://github.com/flutter/flutter/issues/145789#issuecomment-2032968578) still true? Do we just need to wait for a later Flutter update?

Related issue - https://github.com/flutter/flutter/issues/156103

### Steps to reproduce

1. Grab Flutter 3.24.3, Android Gradle Plugin 8.7, and Android Studio Ladybug. Target Java 17.
2. `flutter clean`
3. `flutter build apk`

Tested on Windows. I'm not sure if the OS or Android Studio versions matter.

### Expected results

Clean build

### Actual results

> 3 warnings
> warning: [options] source value 8 is obsolete and will be removed in a future release
> warning: [options] target value 8 is obsolete and will be removed in a future release
> warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.

### Code sample

<details open><summary>Code sample</summary>

See this repo: https://github.com/EnduringBeta/flutter-bug/tree/old-java-version

`app/build.gradle`
```dart
plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'dev.flutter.flutter-gradle-plugin'
    //id 'com.google.gms.google-services'
    //id 'com.google.firebase.crashlytics'
}

// If local properties file doesn't exist, use some default values if possible
def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

// Update Android SDK versions here
// Android SDK levels defined here:
// https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels
def flutterCompileSdkVersion = 35
def flutterMinSdkVersion = 24 // Android 7.0
def flutterTargetSdkVersion = 35

kotlin {
    jvmToolchain(17) // Java version defined here
}

android {
    namespace 'com.example.flutterbug'

    compileSdk flutterCompileSdkVersion

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        applicationId 'com.example.flutterbug'
        minSdkVersion flutterMinSdkVersion
        targetSdkVersion flutterTargetSdkVersion
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    buildTypes {
        debug {
            // This differentiated release from debug build, but it prevented debug build from
            // seeing subscription products. See also `android/app/src/debug/google-services.json`.
            //applicationIdSuffix '.debug'
            debuggable true
        }

        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }

    compileOptions {
        // Flag to enable support for the new language APIs
        coreLibraryDesugaringEnabled true
    }
}

flutter {
    source '../..'
}

dependencies {
    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.1.2'
}
```

`settings.gradle`
```dart
pluginManagement {
    def flutterSdkPath = {
        def properties = new Properties()
        file("local.properties").withInputStream { properties.load(it) }
        def flutterSdkPath = properties.getProperty("flutter.sdk")
        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
        return flutterSdkPath
    }
    settings.ext.flutterSdkPath = flutterSdkPath()

    includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")

    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}

plugins {
    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
    // Update Gradle and Kotlin versions here
    id "com.android.application" version '8.7.0' apply false
    id "org.jetbrains.kotlin.android" version "2.0.20" apply false
    //id "com.google.gms.google-services" version "4.4.2" apply false
    //id "com.google.firebase.crashlytics" version "3.0.2" apply false
    // https://kotlinlang.org/docs/gradle-configure-project.html?utm_campaign=gradle-jvm-toolchain&utm_medium=kgp&utm_source=warnings#gradle-java-toolchains-support
    id "org.gradle.toolchains.foojay-resolver-convention" version "0.8.0"
}

include ":app"
```

</details>


### Screenshots or Video

_No response_

### Logs

<details open><summary>Logs</summary>

```console
$ flutter clean; flutter build apk
Deleting build...                                                1,917ms
Deleting .dart_tool...                                              10ms
Deleting Generated.xcconfig...                                       0ms
Deleting flutter_export_environment.sh...                            0ms
Deleting .flutter-plugins-dependencies...                            0ms
Deleting .flutter-plugins...                                         0ms
Resolving dependencies... 
Downloading packages... 
  collection 1.18.0 (1.19.0 available)
  email_validator 2.1.17 (3.0.0 available)
  http_parser 4.0.2 (4.1.0 available)
  leak_tracker 10.0.5 (10.0.7 available)
  leak_tracker_flutter_testing 3.0.5 (3.0.8 available)
  lints 5.0.0 (5.1.0 available)
  material_color_utilities 0.11.1 (0.12.0 available)
  meta 1.15.0 (1.16.0 available)
  stack_trace 1.11.1 (1.12.0 available)
  string_scanner 1.2.0 (1.3.0 available)
  test_api 0.7.2 (0.7.3 available)
  vm_service 14.2.5 (14.3.0 available)
Got dependencies!
12 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.

Font asset "MaterialIcons-Regular.otf" was tree-shaken, reducing it from 1645184 to 1384 bytes (99.9% reduction). Tree-shaking can be disabled by providing the --no-tree-shake-icons flag when building your app.
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
3 warnings
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
3 warnings
Running Gradle task 'assembleRelease'...                           88.6s
√ Built build\app\outputs\flutter-apk\app-release.apk (39.4MB)
```
</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
$ flutter doctor -v
[√] Flutter (Channel stable, 3.24.3, on Microsoft Windows [Version 10.0.22631.4249], locale en-US)
    • Flutter version 3.24.3 on channel stable at C:\Users\ross\projects\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 2663184aa7 (3 weeks ago), 2024-09-11 16:27:48 -0500
    • Engine revision 36335019a8
    • Dart version 3.5.3
    • DevTools version 2.37.3

[√] Windows Version (Installed version of Windows is version 10 or higher)

[√] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
    • Android SDK at C:\Users\ross\AppData\Local\Android\sdk
    • Platform android-35, build-tools 35.0.0
    • Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
    • Java version OpenJDK Runtime Environment (build 21.0.3+-12282718-b509.11)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

[X] Visual Studio - develop Windows apps
    X Visual Studio not installed; this is necessary to develop Windows apps.
      Download at https://visualstudio.microsoft.com/downloads/.
      Please install the "Desktop development with C++" workload, including all of its default components

[√] Android Studio (version 2024.2)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 21.0.3+-12282718-b509.11)

[√] VS Code (version 1.93.1)
    • VS Code at C:\Users\ross\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension can be installed from:
       https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.22631.4249]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 129.0.6668.71
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 129.0.2792.65

[√] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.
```

</details>


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Android build warnings about Java with latest Gradle: `source value 8 is obsolete`/`target value 8 is obsolete` #156111

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Android build warnings about Java with latest Gradle: source value 8 is obsolete/target value 8 is obsolete #156111

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Android build warnings about Java with latest Gradle: `source value 8 is obsolete`/`target value 8 is obsolete` #156111