mesa: add patch to include driver path in cache key

Mesa usually uses the timestamps of the llvm and driver shared libraries
as a cache key.  In /nix/store these are all zero, so we'll include
$(drivers) in the cache key, which should be unique for all combinations
of mesa and llvm versions.

pkgs/development/libraries/mesa/default.nix

@@ -88,6 +88,7 @@ let self = stdenv.mkDerivation {
   patches = [
     ./symlink-drivers.patch
     ./missing-includes.patch # dev_t needs sys/stat.h, time_t needs time.h, etc.-- fixes build w/musl
+    ./disk_cache-include-dri-driver-path-in-cache-key.patch
   ];
 
   outputs = [ "out" "dev" "drivers" "osmesa" ];