ci: use private setup-ninja action

Author: madebr

.github/workflows/main.yml

@@ -24,6 +24,12 @@ jobs:
         - { name: Macos,             os: macos-latest,   shell: sh,  vendored: false, cmake: '-DSDLIMAGE_DEPS_SHARED=OFF -GNinja', shared: 1, static: 0, artifact: 'SDL3_image-macos' }
 
     steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: ${{ matrix.platform.vendored && 'recursive' }}
+    - name: Set up ninja
+      if: ${{ !contains(matrix.platform.shell, 'msys2') }}
+      uses: ./.github/actions/setup-ninja
 
     - uses: ilammy/msvc-dev-cmd@v1
       if: ${{ matrix.platform.msvc }}
@@ -49,9 +55,6 @@ jobs:
           ${{ matrix.platform.msys-env }}-libtiff
           ${{ matrix.platform.msys-env }}-libwebp
           ${{ matrix.platform.msys-env }}-zlib
-    - name: Install Ninja
-      uses: aseprite/get-ninja@main
-      if: ${{ !contains(matrix.platform.shell, 'msys2') }}
     - name: Set up SDL
       id: sdl
       uses: libsdl-org/setup-sdl@main
@@ -84,10 +87,6 @@ jobs:
       uses: ilammy/setup-nasm@v1
       if: ${{ matrix.platform.vendored && !contains(matrix.platform.shell, 'msys2') }}
 
-    - uses: actions/checkout@v4
-      with:
-        submodules: ${{ matrix.platform.vendored && 'recursive' }}
-
     - name: Check that versioning is consistent
       # We only need to run this once: arbitrarily use the Linux build
       if: ${{ runner.os == 'Linux' }}