fix(android): support AGP 9 built-in Kotlin

[goaly-ai-bot]

Problem

Android Gradle Plugin 9 ships Kotlin support built in and fails the build when a module applies the Kotlin Gradle Plugin on top of it. Any app on AGP 9 that depends on google_api_headers (directly or transitively) cannot build:

A problem occurred evaluating project ':google_api_headers'.
> Failed to apply plugin 'kotlin-android'.
   > ⛔ Failed to apply plugin 'org.jetbrains.kotlin.android'
     The 'org.jetbrains.kotlin.android' plugin is no longer required for Kotlin
     support since AGP 9.0.

AGP 9 also removed android.kotlinOptions.

I hit this in an app that reaches google_api_headers transitively through a place-picker package, where it was the last remaining blocker for the AGP 9 upgrade.

Change

android/build.gradle, compatible with both AGP 8 and AGP 9:

• kotlin-android is applied only when AGP is older than 9, using the same guard the already-migrated plugins use (device_info_plus, share_plus, package_info_plus, wakelock_plus):

  def agpMajor = com.android.Version.ANDROID_GRADLE_PLUGIN_VERSION.tokenize('.')[0] as int
  if (agpMajor < 9) {
      apply plugin: "kotlin-android"
  }

• kotlinOptions { jvmTarget } moves into kotlin { compilerOptions { jvmTarget } }.

No version bumps, no Dart or Kotlin source changes, no behavior change.

Verified

With this patch applied through a path override in a Flutter 3.47.2 app:

Toolchain	Result
AGP 8.12.2 / Gradle 8.14.3	flutter build apk --debug OK
AGP 9.0.1 / Gradle 9.1.0 / android.builtInKotlin=true	flutter build apk --debug OK, flutter build appbundle --release OK

Reference: Built-in Kotlin migration for plugin authors

Happy to adjust style or split it however you prefer.

🤖 Generated with Claude Code

https://claude.ai/code/session_018VxBdp58Dd1HeCZgwFiwkD