fix(android): check the kotlin extension instead of the AGP version

Replace the AGP version / android.builtInKotlin check with a direct test for
the registered kotlin extension. The version check reads
com.android.Version.ANDROID_GRADLE_PLUGIN_VERSION, which can resolve to a
different classpath entry than the AGP actually in use, and the global
android.builtInKotlin property can be overridden per module by the
com.android.built-in-kotlin plugin -- so both inputs can disagree with
reality. Asking whether the kotlin extension exists tests the condition that
actually fails, needs no AGP version table, and covers AGP 10 where the
opt-out is removed.

Co-authored-by: gabrieldonadel <11707729+gabrieldonadel@users.noreply.github.com>

Author: expo-tuft[bot]

android/build.gradle

@@ -22,25 +22,13 @@ def isNewArchitectureEnabled() {
 }
 
 apply plugin: "com.android.library"
-// Android Gradle Plugin 9 ships built-in Kotlin support and applies the Kotlin
-// plugin itself. Applying it a second time fails the configuration phase with
-// "Cannot add extension with name 'kotlin'". Apply it only when AGP is not
-// providing Kotlin: AGP 8 and older, or AGP 9 with android.builtInKotlin=false.
-def shouldApplyKotlinPlugin() {
-  def agpMajor = com.android.Version.ANDROID_GRADLE_PLUGIN_VERSION.tokenize('.')[0].toInteger()
-  if (agpMajor <= 8) {
-    return true
-  }
-  // AGP 10 removes the opt-out: built-in Kotlin is always active there.
-  if (agpMajor >= 10) {
-    return false
-  }
-  def propertyVal = providers.gradleProperty("android.builtInKotlin").orNull
-  def builtInKotlinEnabled = propertyVal != null ? propertyVal.toBoolean() : true
-  return !builtInKotlinEnabled
-}
-
-if (shouldApplyKotlinPlugin()) {
+// AGP 9 ships built-in Kotlin support and registers the `kotlin` extension
+// itself. Applying the Kotlin plugin on top of it fails configuration with
+// "Cannot add extension with name 'kotlin'". Asking for the extension covers
+// every way built-in Kotlin can be turned on -- the global default, the
+// android.builtInKotlin property, and the per-module com.android.built-in-kotlin
+// plugin -- without reading an AGP version number.
+if (project.extensions.findByName('kotlin') == null) {
   apply plugin: "kotlin-android"
 }