Ensure tasks using android sdk or android jar have proper dependencies

A test task, that uses android dependency but does not depend on
a corresponding configuration, would fail when it was run after
'clean' task.
I've extracted 'useAndroidSdk', 'useAndroidJar' extensions
making it harder for a developer to forget to set up task dependencies.

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

@@ -7,10 +7,6 @@ repositories {
     jcenter()
 }
 
-configurations {
-    androidSdk
-}
-
 dependencies {
     testCompile project(':kotlin-gradle-plugin')
     testCompile project(':kotlin-gradle-plugin').sourceSets.test.output
@@ -29,8 +25,6 @@ dependencies {
     testCompile gradleApi()
 
     testRuntime project(path: ':kotlin-android-extensions', configuration: 'runtimeJar')
-
-    androidSdk project(path: ":custom-dependencies:android-sdk", configuration: "androidSdk")
 }
 
 // Include Gradle task properties validation into the testing procedure:
@@ -87,9 +81,8 @@ tasks.withType(Test) {
     if (mavenLocalRepo != null) {
         systemProperty("maven.repo.local", mavenLocalRepo)
     }
-    doFirst {
-        systemProperty("android.sdk", project.configurations["androidSdk"].singleFile.getCanonicalPath())
-    }
+
+    TasksKt.useAndroidSdk(it)
 
     testLogging {
         // set options for log level LIFECYCLE