Add filegroups for services.* libraries

... in preparation for creating a stub library from services.jar

Bug: 139391334
Test: m
Change-Id: Ifd6cfc77acf2284804a2f64011c2733b5c222369
diff --git a/services/usb/Android.bp b/services/usb/Android.bp
index 20855b7..d2c973a 100644
--- a/services/usb/Android.bp
+++ b/services/usb/Android.bp
@@ -1,6 +1,13 @@
+filegroup {
+    name: "services.usb-sources",
+    srcs: ["java/**/*.java"],
+    path: "java",
+    visibility: ["//frameworks/base/services"],
+}
+
 java_library_static {
     name: "services.usb",
-    srcs: ["java/**/*.java"],
+    srcs: [":services.usb-sources"],
 
     libs: [
         "services.core",