Fix github action

.github/workflows/build.yml

@@ -13,26 +13,30 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os:
-          - ubuntu-18.04
-          - windows-latest
+        os: [ubuntu-latest, windows-latest]
         include:
-          - os: ubuntu-18.04
+          - os: ubuntu-latest
             os_short: linux
           - os: windows-latest
             os_short: windows
 
     steps:
 
-      - name: Setup Python 3.8
+      - name: Setup Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
+
+      - name: Checkout AMBuild
+        uses: actions/checkout@v2
+        with:
+          repository: alliedmodders/ambuild
+          path: ambuild
 
       - name: Install AMBuild
-        run: |
-          python -m pip install --upgrade pip setuptools wheel
-          pip install git+https://github.com/alliedmodders/ambuild
+        uses: BSFishy/pip-action@v1
+        with:
+          packages: ./ambuild
 
       - name: Install dependencies (Linux)
         if: runner.os == 'Linux'
@@ -49,6 +53,20 @@ jobs:
           clang --version
           clang++ --version
 
+      - name: Find Visual C++ compilers and make all environment variables global (Windows)
+        if: runner.os == 'Windows'
+        shell: cmd
+        run: |
+          :: See https://github.com/microsoft/vswhere/wiki/Find-VC
+          for /f "usebackq delims=*" %%i in (`vswhere -latest -property installationPath`) do (
+            call "%%i"\Common7\Tools\vsdevcmd.bat -arch=x86 -host_arch=x64
+          )
+
+          :: Loop over all environment variables and make them global.
+          for /f "delims== tokens=1,2" %%a in ('set') do (
+            echo>>"%GITHUB_ENV%" %%a=%%b
+          )
+
       - name: Checkout MetaMod
         uses: actions/checkout@v2
         with: