ci: Install ninja

.github/workflows/build.yml

@@ -43,6 +43,7 @@ jobs:
         Invoke-WebRequest -Uri "https://github.com/mborgerson/xemu-msys2/releases/latest/download/msys64.7z" -OutFile "msys64.7z"
         echo "Extracting MSYS2 environment..."
         7z x -y msys64.7z "-oC:\tools\"
+        C:\tools\msys64\usr\bin\bash.exe -lc "pacman --needed --noconfirm -S mingw-w64-x86_64-ninja"
     # - name: Initialize Compiler Cache
     #   id: cache
     #   uses: actions/cache@v1
@@ -98,7 +99,8 @@ jobs:
           libpixman-1-dev \
           libsdl2-dev \
           libsamplerate0-dev \
-          ccache
+          ccache \
+          ninja-build
     - name: Initialize Compiler Cache
       id: cache
       uses: actions/cache@v1
@@ -163,7 +165,8 @@ jobs:
           pixman \
           pkg-config \
           libsamplerate \
-          sdl2
+          sdl2 \
+          ninja
     - name: Initialize Compiler Cache
       id: cache
       uses: actions/cache@v1