System information (version)

• OpenCV => latest
• Operating System / Platform => Android
• Compiler => Android NDK 22

Detailed description

Build fails with errors like:

NDK is missing a "platforms" directory.
If you are using NDK, verify the ndk.dir is set to a valid NDK directory.  It is currently set to /Users/gilespayne/Library/Android/sdk/ndk/22.0.7026061.
If you are not using NDK, unset the NDK variable from ANDROID_NDK_HOME or local.properties to remove this warning.

….

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':opencv'.
> java.lang.NullPointerException (no error message)

Steps to reproduce

Attempt to build OpenCV for Android with:
./opencv/platforms/android/build_sdk.py --use_android_buildtools --no_samples_build --debug --config ./opencv/platforms/android/ndk-18-api-level-21.config.py

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  forum.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there

Updating the version of ANDROID_GRADLE_PLUGIN_VERSION and the version of Gradle fixes this - I will submit a PR for that