[lavapipe] Required changes for arm64 build of lavapipe.

Change-Id: I83717db71e55eb72f8fb83c2a923fa1cf8f50e8c
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/957192
Reviewed-by: Josh Gargus <jjosh@google.com>
Commit-Queue: John Rosasco <rosasco@google.com>
2 files changed