vulkan/runtime: implement sync file import/export for magma syncobj

Bug:460783239
Change-Id: I7a2f7f5a1bca536e053ac23d96f894ffd1a45198
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/1440599
Commit-Queue: Craig Stout <cstout@google.com>
Reviewed-by: David Gilhooley <dgilhooley@google.com>
1 file changed