Backport av1c generation and add parser-only target am: 01079fdf3c

Original change: https://android-review.googlesource.com/c/platform/external/libgav1/+/2197197

Change-Id: I776eca98526fc88c33b86d50e261caf45e50b4c2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>