Install Ninja using pipx

Author: nightlark

.github/workflows/ci.yml

@@ -26,6 +26,9 @@ jobs:
 
       - uses: actions/checkout@v4
 
+      - name: Install Ninja
+        run: pipx install ninja
+
       - name: Configure (Linux/macOS)
         if: matrix.os != 'windows-latest'
         run: cmake -GNinja -DCMAKE_BUILD_TYPE=Release -Bbuild