Add util method for copying directories

Author: daymxn

buildSrc/src/main/java/com/google/firebase/gradle/plugins/GradleUtils.kt

@@ -0,0 +1,10 @@
+package com.google.firebase.gradle.plugins
+
+import java.io.File
+import org.gradle.api.provider.Provider
+import org.gradle.api.tasks.Copy
+
+fun Copy.fromDirectory(directory: Provider<File>) =
+    from(directory) {
+        into(directory.map { it.nameWithoutExtension })
+    }