Add extra filegroup for telephony related sources

This filegroup is used to obtain extra mappings in the
hiddenapi-mappings target.

Test: m hiddenapi-mappings
Bug: 110868826

(cherry picked from commit 740f28fe640ad3db68effaf3ce0974737d2418e6)

Change-Id: Iedc489842dad99099173f5087b0f94a90641ae8a
Merged-In: I0771603eeaa7c597b730802d2d8d40efcfff827c
diff --git a/Android.bp b/Android.bp
index 79de990..d1a8937 100644
--- a/Android.bp
+++ b/Android.bp
@@ -27,6 +27,13 @@
     ],
 }
 
+filegroup {
+    name: "opt-telephony-common-srcs",
+    srcs: [
+        "src/java/**/*.java",
+    ],
+}
+
 java_library {
     name: "telephony-common",
     installable: true,
@@ -35,7 +42,7 @@
         local_include_dirs: ["src/java"],
     },
     srcs: [
-        "src/java/**/*.java",
+        ":opt-telephony-common-srcs",
         "src/java/**/I*.aidl",
         "src/java/**/*.logtags",
     ],