gradle-plugin: Add root konanCompile task to compile all artifacts

samples/concurrent/build.gradle

@@ -11,4 +11,13 @@ konanArtifacts {
         useInterop "MessageChannel"
         nativeLibrary "${project.buildDir.canonicalPath}/clang/MessageChannel.bc"
     }
+}
+
+task compileCpp(type: Exec) {
+    workingDir project.getProjectDir()
+    commandLine './buildCpp.sh'
+}
+
+genMessageChannelInteropStubs {
+    dependsOn(compileCpp)
 }

samples/tetris/build.gradle

@@ -65,7 +65,7 @@ konanArtifacts {
     }
 }
 
-build {
+compileKonan {
     project.ext {
         buildTasks = getTaskDependencies().getDependencies().findAll { task -> task.name.startsWith("compileKonan") }
     }

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KonanPlugin.kt

@@ -197,13 +197,13 @@ class KonanPlugin @Inject constructor(private val registry: ToolingModelBuilderR
      * Looks for task with given name in the given project.
      * If such task isn't found, will create it. Returns created/found task.
      */
-    private fun getTask(project: ProjectInternal, name: String): Task = project.getTasksByName(name, false).single()
+    private fun ProjectInternal.getTask(name: String): Task = getTasksByName(name, false).single()
 
-    private fun getOrCreateTask(project: ProjectInternal, name: String): Task {
-        var tasks = project.getTasksByName(name, false)
+    private fun ProjectInternal.getOrCreateTask(name: String): Task {
+        var tasks = getTasksByName(name, false)
         assert(tasks.size <= 1)
         return if (tasks.isEmpty()) {
-            project.tasks.create(name, DefaultTask::class.java)
+            this.tasks.create(name, DefaultTask::class.java)
         } else {
             tasks.single()
         }
@@ -223,12 +223,15 @@ class KonanPlugin @Inject constructor(private val registry: ToolingModelBuilderR
         if (!project.extensions.extraProperties.has(KonanPlugin.KONAN_BUILD_TARGETS)) {
             project.extensions.extraProperties.set(KonanPlugin.KONAN_BUILD_TARGETS, project.host)
         }
-        getTask(project, "build").apply {
+        val compileKonanTask = project.getOrCreateTask("compileKonan").apply {
             dependsOn(project.supportedCompileTasks)
         }
+        project.getTask("build").apply {
+            dependsOn(compileKonanTask)
+        }
 
-        getOrCreateTask(project, "run").apply {
-            dependsOn(getTask(project, "build"))
+        project.getOrCreateTask("run").apply {
+            dependsOn(project.getTask("build"))
             doLast {
                 for (task in project.tasks.withType(KonanCompileTask::class.java).matching { !it.isCrossCompile}) {
                     if (task?.produce == "program") {