[Infra] Update how we declare kotlin compiler options

Kotlin compiler options should be specified using the kotlin block
instead of the `kotlinOptions` within `android`. See
https://youtrack.jetbrains.com/issue/KT-27301/Expose-compiler-flags-via-Gradle-lazy-properties
and https://b.corp.google.com/issues/247544167. This applies to how
the JVM target is declared.

Additionally, there's a better way to declare free compiler args, in
our case to forche the explicit api flag to be "strict".

Author: rlazo

firebase-ai/firebase-ai.gradle.kts

@@ -16,7 +16,8 @@
 
 @file:Suppress("UnstableApiUsage")
 
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinJvmCompile
 
 plugins {
   id("firebase-library")
@@ -55,7 +56,6 @@ android {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
   }
-  kotlinOptions { jvmTarget = "1.8" }
   testOptions {
     targetSdk = targetSdkVersion
     unitTests {
@@ -73,17 +73,17 @@ android {
   }
 }
 
+kotlin { compilerOptions { jvmTarget = JvmTarget.JVM_1_8 } }
+
 // Enable Kotlin "Explicit API Mode". This causes the Kotlin compiler to fail if any
 // classes, methods, or properties have implicit `public` visibility. This check helps
 // avoid  accidentally leaking elements into the public API, requiring that any public
 // element be explicitly declared as `public`.
 // https://github.com/Kotlin/KEEP/blob/master/proposals/explicit-api-mode.md
 // https://chao2zhang.medium.com/explicit-api-mode-for-kotlin-on-android-b8264fdd76d1
-tasks.withType<KotlinCompile>().all {
+tasks.withType<KotlinJvmCompile>().configureEach {
   if (!name.contains("test", ignoreCase = true)) {
-    if (!kotlinOptions.freeCompilerArgs.contains("-Xexplicit-api=strict")) {
-      kotlinOptions.freeCompilerArgs += "-Xexplicit-api=strict"
-    }
+    compilerOptions.freeCompilerArgs.add("-Xexplicit-api=strict")
   }
 }
 

firebase-functions/firebase-functions.gradle.kts

@@ -1,5 +1,3 @@
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
-
 // Copyright 2022 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
@@ -14,6 +12,9 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinJvmCompile
+
 plugins {
   id("firebase-library")
   id("kotlin-android")
@@ -49,25 +50,24 @@ android {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
   }
-  kotlinOptions { jvmTarget = "1.8" }
   testOptions {
     targetSdk = targetSdkVersion
     unitTests { isIncludeAndroidResources = true }
   }
   lint { targetSdk = targetSdkVersion }
 }
 
+kotlin { compilerOptions { jvmTarget = JvmTarget.JVM_1_8 } }
+
 // Enable Kotlin "Explicit API Mode". This causes the Kotlin compiler to fail if any
 // classes, methods, or properties have implicit `public` visibility. This check helps
 // avoid  accidentally leaking elements into the public API, requiring that any public
 // element be explicitly declared as `public`.
 // https://github.com/Kotlin/KEEP/blob/master/proposals/explicit-api-mode.md
 // https://chao2zhang.medium.com/explicit-api-mode-for-kotlin-on-android-b8264fdd76d1
-tasks.withType<KotlinCompile>().all {
+tasks.withType<KotlinJvmCompile>().configureEach {
   if (!name.contains("test", ignoreCase = true)) {
-    if (!kotlinOptions.freeCompilerArgs.contains("-Xexplicit-api=strict")) {
-      kotlinOptions.freeCompilerArgs += "-Xexplicit-api=strict"
-    }
+    compilerOptions.freeCompilerArgs.add("-Xexplicit-api=strict")
   }
 }
 

firebase-sessions/firebase-sessions.gradle.kts

@@ -16,6 +16,9 @@
 
 @file:Suppress("UnstableApiUsage")
 
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinJvmCompile
+
 plugins {
   id("firebase-library")
   id("firebase-vendor")
@@ -49,7 +52,6 @@ android {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
   }
-  kotlinOptions { jvmTarget = "1.8" }
   testOptions {
     targetSdk = targetSdkVersion
     unitTests { isIncludeAndroidResources = true }
@@ -60,8 +62,12 @@ android {
   }
 }
 
-tasks.withType(org.jetbrains.kotlin.gradle.tasks.KaptGenerateStubs::class.java).configureEach {
-  kotlinOptions.jvmTarget = "1.8"
+kotlin { compilerOptions { jvmTarget = JvmTarget.JVM_1_8 } }
+
+tasks.withType<KotlinJvmCompile>().configureEach {
+  if (!name.contains("test", ignoreCase = true)) {
+    compilerOptions.freeCompilerArgs.add("-Xexplicit-api=strict")
+  }
 }
 
 dependencies {