Add filegroup for trout project to use VehicleHalProto definition

Other virtualization specific definitions and build rules will be moved
to /device/google/trout in the following patches. Keep them for now so
that we will not break the build.

Test: build
Bug: 148816426
Change-Id: I8a579346b55aa812db3dd30a34050c9515f7a68d
diff --git a/automotive/vehicle/2.0/default/impl/vhal_v2_0/proto/Android.bp b/automotive/vehicle/2.0/default/impl/vhal_v2_0/proto/Android.bp
index 2eedecd..9784f75 100644
--- a/automotive/vehicle/2.0/default/impl/vhal_v2_0/proto/Android.bp
+++ b/automotive/vehicle/2.0/default/impl/vhal_v2_0/proto/Android.bp
@@ -27,7 +27,17 @@
         "-Wall",
         "-Werror",
     ],
-    srcs: ["VehicleHalProto.proto"]
+    srcs: ["VehicleHalProto.proto"],
+}
+
+filegroup {
+    name: "vhal-proto-src",
+    visibility: [
+        "//device/google/trout/hal/vehicle/2.0:__subpackages__",
+    ],
+    srcs: [
+        "VehicleHalProto.proto",
+    ],
 }
 
 cc_library_static {
@@ -49,7 +59,7 @@
         "libgrpc++_unsecure",
     ],
     cflags: [
-        "-Wno-unused-parameter"
+        "-Wno-unused-parameter",
     ],
 }