CI: Add C preproc indentation check to CI

closes: #19165

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/MAINTAINERS

@@ -699,6 +699,7 @@ runtime/syntax/xs.vim					@petdance
 runtime/syntax/xslt.vim					@Boobies
 runtime/syntax/zserio.vim				@dpelle
 runtime/syntax/zsh.vim					@chrisbra
+runtime/tools/preproc_indent.vim			@h-east
 runtime/tutor/tutor1.eo					@dpelle
 runtime/tutor/tutor1.fr					@dpelle
 runtime/tutor/tutor1.ru					@RestorerZ

.github/workflows/ci.yml

@@ -84,7 +84,7 @@ jobs:
             architecture: arm64
           - features: normal
             compiler: gcc
-            extra: [vimtags, proto]
+            extra: [vimtags, proto, preproc_indent]
           - features: huge
             compiler: gcc
             extra: [no_x11_wl]
@@ -363,6 +363,16 @@ jobs:
             true
           )
 
+      - name: Check preprocessor indent
+        if: contains(matrix.extra, 'preproc_indent')
+        run: |
+          # This will exit with an error code if the files differ from source
+          (
+            "${SRCDIR}"/vim -u NONE --not-a-term -esNX +"cd runtime/tools" -S preproc_indent.vim
+            git diff --exit-code -- src/*.[ch] src/xxd/xxd.c
+            true
+          )
+
       - name: Generate gcov files
         if: matrix.coverage
         run: |