Use default compileJava9Java task to build java9 source set

libraries/commonConfiguration.gradle

@@ -52,6 +52,30 @@ ext.configureJvm6Project = { Project project ->
     }
 }
 
+ext.compileJava9Sources = { Project project, String moduleName, Collection<FileCollection> moduleOutputs = [project.sourceSets.main.output] ->
+    // module-info.java should be in java9 source set by convention
+    SourceDirectorySet java9SourceSet = project.sourceSets.java9.java
+    project.tasks.getByName("compileJava9Java").configure { JavaCompile it ->
+        dependsOn(moduleOutputs)
+        it.sourceCompatibility = 1.9
+        it.targetCompatibility = 1.9
+        it.destinationDir = file("${java9SourceSet.outputDir}/META-INF/versions/9")
+        it.options.fork = true
+        it.options.forkOptions.javaHome = file(JDK_9)
+        it.options.sourcepath = files(java9SourceSet.srcDirs)
+
+        doFirst {
+            def moduleFiles = moduleOutputs.collect { it.files }.flatten().join(File.pathSeparator)
+
+            options.compilerArgs = [
+                    '--module-path', project.configurations.compileClasspath.asPath,
+                    '--patch-module', "$moduleName=$moduleFiles"
+            ]
+            classpath = files()
+        }
+    }
+}
+
 ext.manifestAttributes = { Manifest manifest, Project project, String component = null, boolean multiRelease = false ->
     project.configure(manifest) {
         attributes \
@@ -202,33 +226,3 @@ ext.createPreprocessorTask = { Project project, def name, def sourceDir, def tar
         args = [sourceDir, targetDir, profile]
     }
 }
-
-ext.createCompileJava9Task = { Project project, String name, String moduleName, List<? extends FileCollection> extraModuleContent = [] ->
-    project.tasks.findByName("compileJava9Java").enabled = false
-
-    def task = project.tasks.create(name, Exec)
-
-    def sourceSet = project.sourceSets.java9.java
-    task.inputs.dir(sourceSet.srcDirs.first())
-    task.outputs.dir(sourceSet.outputDir)
-
-    task.dependsOn(project.tasks.findByName("compileKotlin"), project.tasks.findByName("compileJava"))
-
-    def moduleContent = project.sourceSets.main.output.join(File.pathSeparator)
-    for (collection in extraModuleContent) {
-        moduleContent += File.pathSeparator + collection.asPath
-    }
-
-    def output = new File(sourceSet.outputDir, "META-INF/versions/9")
-
-    task.doFirst {
-        output.delete()
-        output.mkdirs()
-    }
-
-    task.commandLine = ["${JDK_9}/bin/javac",
-                        *fileTree(sourceSet.srcDirs.first()).files.toArray(),
-                        "-d", output.path,
-                        "-p", project.configurations.compile.asPath,
-                        "--patch-module", "$moduleName=$moduleContent"]
-}