ci: use meson to run clang-format

This will allow us to easily exclude vendored code when we enforce the
formatting of more components later on.

Signed-off-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23269>

.gitlab-ci/test-source-dep.yml

@@ -994,6 +994,9 @@
    rules:
     - !reference [.core-rules, rules]
     - changes:
+      - .clang-format
+      - .clang-format-include
+      - .clang-format-ignore
       - src/**/asahi/**/*
       - src/**/panfrost/**/*
       when: on_success

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

@@ -42,9 +42,10 @@ clang-format:
     LLVM_VERSION: 15
   script:
     - shopt -s globstar
-    - clang-format-${LLVM_VERSION:?} --Werror -i
-      src/**/asahi/**/*.{h,c,cpp}
-      src/**/panfrost/**/*.{h,c,cpp}
+    # We need a meson build dir, but its config doesn't actually matter, so
+    # let's just use the default.
+    - meson setup build
+    - ninja -C build clang-format
     - git diff --color=always --exit-code  # Fails if there are diffs
 
 .test-gl: