gfxstream-protocols: allow generating outside of AOSP am: dffb09bb1d am: 8d43b69c23

Original change: https://android-review.googlesource.com/c/platform/external/gfxstream-protocols/+/2260366

Change-Id: If02a9d35a6156289a3845e32e635110a62d1a4d9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>