Meta: Add gn linter

This just calls ``gn format`` on any .gn or .gni files, but it matches
the pattern of the other linters.

.github/workflows/cmake.yml

@@ -59,7 +59,7 @@ jobs:
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
           sudo add-apt-repository 'deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-16 main'
           sudo apt-get update
-          sudo apt-get install -y clang-format-16 ccache e2fsprogs gcc-12 g++-12 libstdc++-12-dev libmpfr-dev libmpc-dev ninja-build optipng qemu-utils qemu-system-i386 unzip
+          sudo apt-get install -y clang-format-16 ccache e2fsprogs gcc-12 g++-12 libstdc++-12-dev libmpfr-dev libmpc-dev ninja-build optipng qemu-utils qemu-system-i386 unzip generate-ninja
           if ${{ matrix.arch == 'aarch64' }}; then
             # FIXME: Remove this when we no longer build our own Qemu binary.
             sudo apt-get install libgtk-3-dev libpixman-1-dev libsdl2-dev libslirp-dev
@@ -72,7 +72,7 @@ jobs:
           python -m pip install --upgrade pip
           pip install flake8 requests
       - name: Check versions
-        run: set +e; g++ --version; g++-12 --version; clang-format --version; clang-format-16 --version; prettier --version; python --version; python3 --version; ninja --version; flake8 --version; ccache --version; qemu-system-i386 --version
+        run: set +e; g++ --version; g++-12 --version; clang-format --version; clang-format-16 --version; prettier --version; python --version; python3 --version; ninja --version; flake8 --version; ccache --version; qemu-system-i386 --version; gn --version
 
       # === PREPARE FOR BUILDING ===
 

Meta/lint-ci.sh

@@ -29,6 +29,7 @@ for cmd in \
         Meta/check-style.py \
         Meta/lint-executable-resources.sh \
         Meta/lint-gml-format.sh \
+        Meta/lint-gn.sh \
         Meta/lint-keymaps.py \
         Meta/lint-prettier.sh \
         Meta/lint-python.sh \

Meta/lint-gn.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+set -e
+
+script_path=$(cd -P -- "$(dirname -- "$0")" && pwd -P)
+cd "${script_path}/.." || exit 1
+
+if [ "$#" -eq "0" ]; then
+    mapfile -t files < <(
+        git ls-files '*.gn' '*.gni'
+    )
+else
+    files=()
+    for file in "$@"; do
+        if [[ "${file}" == *".gn" ]] || [[ "${file}" == *".gni" ]]; then
+            files+=("${file}")
+        fi
+    done
+fi
+
+if (( ${#files[@]} )); then
+    if ! command -v gn >/dev/null 2>&1 ; then
+        echo "gn is not available, but gn files need linting! Either skip this script, or install gn."
+        exit 1
+    fi
+    gn format "${files[@]}"
+else
+    echo "No .gn or .gni files to check."
+fi