fix(mesa)

closes #4616

projects/mesa3d.org/package.yml

@@ -103,6 +103,7 @@ test:
     freedesktop.org/pkg-config: '*'
     linux:
       gnu.org/gcc: '*' # archlinux doesn't provide libgcc
+      llvm.org: '*'
   env:
     FLAGS:
       - -lX11
@@ -112,10 +113,8 @@ test:
       FLAGS:
         - -lGl
     linux:
-      CC: clang
-      AS: llvm-as
       FLAGS:
         - '{{prefix}}/lib/libGL.so.1'
   script:
-    - cc glxgears.c -o gears $FLAGS
+    - clang glxgears.c -o gears $FLAGS
     - pkg-config --modversion gl | grep {{version}}