ci: color the diff for clang-format

Suggested-by: David Heidelberg <[email protected]>
Signed-off-by: Eric Engestrom <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23269>

Author: 1ace

.gitlab-ci/test/gitlab-ci.yml

@@ -45,7 +45,7 @@ clang-format:
     - clang-format-${LLVM_VERSION:?} --Werror -i
       src/**/asahi/**/*.{h,c,cpp}
       src/**/panfrost/**/*.{h,c,cpp}
-    - git diff --exit-code  # Fails if there are diffs
+    - git diff --color=always --exit-code  # Fails if there are diffs
 
 .test-gl:
   extends: