Add source_set for external access to drm headers

Bug:71878

Change-Id: I90ee8971f824868cfc8179fe7e03c7a44736bd9a
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/497858
Reviewed-by: John Bauman <jbauman@google.com>
1 file changed