Gradle build fixes & improvements:

* Fix Java not compiled in kotlin-gradle-plugin Kotlin source set
* Fix the integration tests running under Java 6
* Fix kotlin-gradle-subplugin-example not being installed -- needed
  for a test
* Fix Android tests being always excluded
* Move versions out of `build.gradle` (x2) to a common `versions.gradle`
* Move JDK, dist and bootstrap to `commonConfiguration.gradle`
* Build `kotlin-gradle-plugin` with JDK_18

libraries/tools/gradle-tools/build.gradle

@@ -1,7 +1,6 @@
 buildscript {
-    ext.kotlin_version = findProperty("deployVersion") ?: "1.1-SNAPSHOT"
-    ext.kotlin_language_version = "1.1"
-    ext.kotlin_gradle_plugin_version = findProperty("kotlinGradlePluginVersion") ?: "1.1.1"
+    ext.kotlin_root = findProperty("kotlinRoot") ?: "${rootProject.projectDir}/../../.."
+    apply from: "${kotlin_root}/libraries/versions.gradle"
 
     repositories {
         mavenCentral()
@@ -11,19 +10,8 @@ buildscript {
     }
 }
 
-ext.kotlin_root = findProperty("kotlinRoot") ?: "${rootProject.projectDir}/../../.."
-
 apply from: "${kotlin_root}/libraries/commonConfiguration.gradle"
 
-ext {
-    JDK_16 = jdkPath("1.6")
-    JDK_17 = jdkPath("1.7")
-    JDK_18 = jdkPath("1.8")
-    distDir = file("${kotlin_root}/dist")
-    distLibDir = file("${kotlin_root}/dist/kotlinc/lib")
-    bootstrapCompilerFile = file("$distDir/kotlin-compiler-for-maven.jar")
-}
-
 allprojects {
     group = 'org.jetbrains.kotlin'
     version = "$kotlin_version"

libraries/tools/kotlin-gradle-plugin-integration-tests/build.gradle

@@ -8,8 +8,6 @@ repositories {
     maven { url 'http://repository.jetbrains.com/utils/' }
 }
 
-def kotlinVersion = project.version
-
 dependencies {
     testCompile project(':kotlin-gradle-plugin')
     testCompile project(':kotlin-gradle-plugin').sourceSets.test.output
@@ -30,7 +28,11 @@ processResources {
 tasks.withType(Test) {
     onlyIf { !project.hasProperty("noTest") }
 
-    exclude '**/KotlinAndroid*'
+    if (!project.hasProperty("android")) {
+        exclude '**/KotlinAndroid*'
+    }
+
+    executable = "${JDK_18}/bin/java"
 
     testLogging {
         // set options for log level LIFECYCLE

libraries/tools/kotlin-gradle-plugin/build.gradle

@@ -41,6 +41,10 @@ dependencies {
     testCompile "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
 }
 
+tasks.withType(project.compileKotlin.class) {
+    kotlinOptions.jdkHome = JDK_18
+}
+
 compileKotlin.dependsOn compileGroovy
 compileGroovy.dependsOn.remove("compileJava")
 
@@ -48,6 +52,7 @@ def groovyClassesDir = file("${buildDir}/mainGroovyClasses")
 compileGroovy.destinationDir = groovyClassesDir
 sourceSets.main.compileClasspath += files(groovyClassesDir)
 compileGroovy.classpath = sourceSets.main.compileClasspath - files(groovyClassesDir)
+sourceSets.main.java.srcDirs += sourceSets.main.kotlin.srcDirs
 
 processResources {
     expand(project.properties)