scons: Fix grpc protobuf actions

The change will fix the proto import issue and build issue with
--no-duplicate-sources options, more details please reference:
https://gem5-review.googlesource.com/c/public/gem5/+/64491.

Change-Id: I259413f7739f89598dcd42c3f2e1e865cec3de43
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71318
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71338
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
1 file changed