Sandbox-copied protos are not used in compilation

[Max Vorobev]

python_grpc_compile fails to compile generated .proto file (it's copied into sandbox, but not used in compilation)

Example can be found here: vmax/org_pubref_rules_proto_bug_sample

ghost:rules_proto_example vmax$ bazel build //:routeguide_gen_grpc
INFO: Analysed target //:routeguide_gen_grpc (0 packages loaded).
INFO: Found 1 target...
ERROR: /Users/vmax/work/GraknLabs/rules_proto_example/BUILD:35:1: error executing shell command: 'bazel-out/host/bin/external/com_google_protobuf/protoc --descriptor_set_out=bazel-out/darwin-fastbuild/genfiles/routeguide_gen_grpc/descriptor.source.bin --proto_path=bazel-out/darwin-fastbuild/gen...' failed (Exit 1)
bazel-out/darwin-fastbuild/genfiles/routeguide_gen.proto: No such file or directory
Target //:routeguide_gen_grpc failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0,235s, Critical Path: 0,05s
INFO: 0 processes.
FAILED: Build did NOT complete successfully