Use soong_java_prebuilt.mk to export soong jars to java

Instead of trying to squeeze soong jars through prebuilt_internal.mk,
make a separate soong_java_prebuilt.mk.

Test: m -j checkbuild
Change-Id: Idadef3c21a6f618d573110f04c80d7db3db92031
diff --git a/java/androidmk.go b/java/androidmk.go
index c383a0e..49f58df 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -26,6 +26,7 @@
 	return android.AndroidMkData{
 		Class:      "JAVA_LIBRARIES",
 		OutputFile: android.OptionalPathForPath(library.outputFile),
+		Include:    "$(BUILD_SYSTEM)/soong_java_prebuilt.mk",
 		Extra: []android.AndroidMkExtraFunc{
 			func(w io.Writer, outputFile android.Path) {
 				fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := .jar")
@@ -41,6 +42,7 @@
 	return android.AndroidMkData{
 		Class:      "JAVA_LIBRARIES",
 		OutputFile: android.OptionalPathForPath(prebuilt.combinedClasspathFile),
+		Include:    "$(BUILD_SYSTEM)/soong_java_prebuilt.mk",
 		Extra: []android.AndroidMkExtraFunc{
 			func(w io.Writer, outputFile android.Path) {
 				fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := .jar")
@@ -54,6 +56,7 @@
 	return android.AndroidMkData{
 		Class:      "JAVA_LIBRARIES",
 		OutputFile: android.OptionalPathForPath(binary.outputFile),
+		Include:    "$(BUILD_SYSTEM)/soong_java_prebuilt.mk",
 		SubName:    ".jar",
 		Custom: func(w io.Writer, name, prefix, moduleDir string, data android.AndroidMkData) {
 			android.WriteAndroidMkData(w, data)