Speed up the pipeline by using Ninja

.github/workflows/build.yml

@@ -10,13 +10,20 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [windows-2019, macos-10.15, ubuntu-20.04]
+        os: [windows-2022, macos-11, ubuntu-20.04]
     env:
-      BUILD_TYPE: Release
+      BUILD_TYPE: 'Release'
+      CMAKE_GENERATOR: 'Ninja'
     steps:
     - name: Checkout
       uses: actions/checkout@v3
 
+    - name: Install Ninja
+      uses: seanmiddleditch/gha-setup-ninja@6263846cf3c17009dfc81604efabae16044fc074 # master
+
+    - name: Visual Studio Development Environment
+      uses: ilammy/msvc-dev-cmd@cec98b9d092141f74527d0afa6feb2af698cfe89 # v1.12.1
+
     - name: Tag cmkr.cmake
       if: ${{ startsWith(github.ref, 'refs/tags/') }}
       run: cmake -P "cmake/replace_tag.cmake"

src/cmake_generator.cpp

@@ -8,6 +8,7 @@
 #include <memory>
 #include <sstream>
 #include <stdexcept>
+#include <fstream>
 
 namespace cmkr {
 namespace gen {