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

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

Change-Id: Ia17085b938458953846f59256c88feb8f1a86be5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>