The Bug

In FlutterPlugin.kt , we register the directory containing Flutter's intermediate JNI libraries (like libapp.so ) to the Android source set so Gradle knows to package them:

val jniLibsDir: Provider<Directory> = ...                                                                                                                                                                
sourceSet.jniLibs.srcDir(jniLibsDir.get().asFile) // <-- The Bug                                                                                                                                         

1. Eager Evaluation: Calling .get().asFile on jniLibsDir (which is a lazy Gradle Provider ) forces Gradle to resolve the path immediately during the Configuration Phase. At this point, it resolves
   to the default path (e.g., build/intermediates/flutter/... ).
2. Delayed Customization: If the project (or a plugin) customizes the build directory later in the configuration (e.g., layout.buildDirectory.set("custom_build_dir") ), Gradle updates the layout.
   buildDirectory property.
3. The Mismatch:
   • Writing: The Flutter task that copies libapp.so uses the lazy jniLibsDir provider, so it correctly resolves the path at Execution Phase and writes the library to the custom directory (
   custom_build_dir/intermediates/... ).
   • Reading: The Android packaging task reads from the source set we registered earlier. Because we passed a static File resolved eagerly, it looks in the default directory ( build/intermediates/...
   ), which is empty.
   • As a result, libapp.so is silently left out of the final APK/AAB.

──────

The Fix

The fix changes the registration to pass the lazy Provider directly:

-            sourceSet.jniLibs.srcDir(jniLibsDir.get().asFile)                                                                                                                                           
+            sourceSet.jniLibs.srcDir(jniLibsDir)                                                                                                                                                        

1. Lazy Evaluation: Gradle's srcDir() API natively accepts Provider objects. By passing jniLibsDir directly without calling .get() , we keep it lazy.
2. Deferred Resolution: Gradle now defers resolving the actual path until the Execution Phase (when it actually needs to read the files).
3. Alignment: Both the task that writes libapp.so and the packaging task that reads it now resolve the jniLibsDir provider at the same time, ensuring they both point to the customized
   custom_build_dir path.

Fixes: #186810

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
• All existing and new tests are passing.