build: Introduce Kotlin Gradle Convention Plugin

`kotlin-jvm` is intended for our modules which target `java-library`

Issue 20775

Assisted-by: Claude Opus 4.7

Author: david-allison

buildSrc/src/main/kotlin/ankidroid.kotlin-jvm.gradle.kts

@@ -0,0 +1,36 @@
+/*
+ *  Copyright (c) 2026 David Allison <davidallisongithub@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// Convention plugin: applies the Kotlin JVM plugin and pins Java/Kotlin
+// toolchain settings for pure-JVM (non-Android) modules in this project.
+
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+    id("org.jetbrains.kotlin.jvm")
+}
+
+tasks.withType(JavaCompile::class).configureEach {
+    sourceCompatibility = JavaVersion.VERSION_17.toString()
+    targetCompatibility = JavaVersion.VERSION_17.toString()
+}
+
+tasks.withType(KotlinCompile::class).configureEach {
+    compilerOptions {
+        jvmTarget = JvmTarget.JVM_17
+    }
+}

common/build.gradle.kts

@@ -1,22 +1,8 @@
-import org.jetbrains.kotlin.gradle.dsl.JvmTarget
-
 plugins {
-    // Use `id` to avoid classpath conflicts. Versions are pinned by buildSrc/.
-    id("org.jetbrains.kotlin.jvm")
+    id("ankidroid.kotlin-jvm")
     `java-test-fixtures`
 }
 
-java {
-    sourceCompatibility = JavaVersion.VERSION_17
-    targetCompatibility = JavaVersion.VERSION_17
-}
-
-kotlin {
-    compilerOptions {
-        jvmTarget = JvmTarget.JVM_17
-    }
-}
-
 dependencies {
     implementation(libs.json)
     implementation(libs.androidx.annotation)

lint-rules/build.gradle.kts

@@ -1,19 +1,5 @@
-import org.jetbrains.kotlin.gradle.dsl.JvmTarget
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
-
 plugins {
-    id("kotlin")
-}
-
-tasks.withType(JavaCompile::class).configureEach {
-    sourceCompatibility = JavaVersion.VERSION_17.toString()
-    targetCompatibility = JavaVersion.VERSION_17.toString()
-}
-
-tasks.withType(KotlinCompile::class).all {
-    compilerOptions {
-        jvmTarget = JvmTarget.JVM_17
-    }
+    id("ankidroid.kotlin-jvm")
 }
 
 dependencies {