[4.4] CI: Show doctool diffs inside submodules

Author: aaronfranke

.github/workflows/linux_builds.yml

@@ -225,7 +225,7 @@ jobs:
           echo "Running --doctool to see if this changes the public API without updating the documentation."
           echo -e "If a diff is shown, it means that your code/doc changes are incomplete and you should update the class reference with --doctool.\n\n"
           ${{ matrix.bin }} --doctool --headless 2>&1 > /dev/null || true
-          git diff --color --exit-code && ! git ls-files --others --exclude-standard | sed -e 's/^/New doc file missing in PR: /' | grep 'xml$'
+          git diff --color --submodule=diff --ignore-submodules=none --exit-code && ! git ls-files --others --exclude-standard | sed -e 's/^/New doc file missing in PR: /' | grep 'xml$'
 
       # Check API backwards compatibility
       - name: Check for GDExtension compatibility