Add _mock files to output list of generate_cc.bzl
diff --git a/bazel/generate_cc.bzl b/bazel/generate_cc.bzl
index 72fc609..d979b76 100644
--- a/bazel/generate_cc.bzl
+++ b/bazel/generate_cc.bzl
@@ -12,6 +12,8 @@
   if ctx.executable.plugin:
     outs += [proto.basename[:-len(".proto")] + ".grpc.pb.h" for proto in protos]
     outs += [proto.basename[:-len(".proto")] + ".grpc.pb.cc" for proto in protos]
+    if ctx.attr.generate_mock:
+      outs += [proto.basename[:-len(".proto")] + "_mock.grpc.pb.h" for proto in protos]
   else:
     outs += [proto.basename[:-len(".proto")] + ".pb.h" for proto in protos]
     outs += [proto.basename[:-len(".proto")] + ".pb.cc" for proto in protos]