Github: Adds mingw build test workflow

Currently only does a build, doing a CI run means figuring out why
TestHarnessRunner doesn't find libraries correctly.

I want to ensure we don't break building at least while sorting out the
rest of this.

.github/workflows/mingw_build.yml

@@ -0,0 +1,96 @@
+name: Mingw build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+env:
+  BUILD_TYPE: Debug
+  FEX_ENABLEAVX: 1
+
+jobs:
+  build:
+    runs-on: ${{ matrix.arch }}
+    strategy:
+      matrix:
+        arch: [[self-hosted, x64, mingw], [self-hosted, ARM64, mingw]]
+      fail-fast: false
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set runner label
+      run: echo "runner_label=${{ matrix.arch[1] }}" >> $GITHUB_ENV
+
+    - name: Set CC x86
+      if: matrix.arch[1] == 'x64'
+      run: |
+        echo "CC=$HOME/llvm-mingw/build/bin/x86_64-w64-mingw32-clang" >> $GITHUB_ENV
+        echo "CXX=$HOME/llvm-mingw/build/bin/x86_64-w64-mingw32-clang++" >> $GITHUB_ENV
+
+    - name: Set CC Arm64
+      if: matrix.arch[1] == 'ARM64'
+      run: |
+        echo "CC=$HOME/llvm-mingw/build/bin/aarch64-w64-mingw32-clang" >> $GITHUB_ENV
+        echo "CXX=$HOME/llvm-mingw/build/bin/aarch64-w64-mingw32-clang++" >> $GITHUB_ENV
+
+    - name: Set rootfs paths
+      run: |
+        echo "FEX_ROOTFS_MOUNT=/mnt/AutoNFS/rootfs/" >> $GITHUB_ENV
+        echo "FEX_ROOTFS_PATH=$HOME/Rootfs/" >> $GITHUB_ENV
+        echo "FEX_ROOTFS=$HOME/Rootfs/" >> $GITHUB_ENV
+        echo "ROOTFS=$HOME/Rootfs/" >> $GITHUB_ENV
+
+    - name: Update RootFS cache
+      # Use a bash shell so we can use the same syntax for environment variable
+      # access regardless of the host operating system
+      shell: bash
+      run: $GITHUB_WORKSPACE/Scripts/CI_FetchRootFS.py
+
+    - name : submodule checkout
+      # Need to update submodules
+      run: |
+        git submodule sync --recursive
+        git submodule update --init --depth 1
+
+    - name: Clean Build Environment
+      run: rm -Rf ${{runner.workspace}}/build
+
+    - name: Create Build Environment
+      # Some projects don't allow in-source building, so create a separate build directory
+      # We'll use this as our working directory for all subsequent commands
+      run: cmake -E make_directory ${{runner.workspace}}/build
+
+    - name: Configure CMake
+      # Use a bash shell so we can use the same syntax for environment variable
+      # access regardless of the host operating system
+      shell: bash
+      working-directory: ${{runner.workspace}}/build
+      # Note the current convention is to use the -S and -B options here to specify source
+      # and build directories, but this is only available with CMake 3.13 and higher.
+      # The CMake binaries on the Github Actions machines are (as of this writing) 3.12
+      run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE -G Ninja -DENABLE_LTO=False -DENABLE_ASSERTIONS=True -DENABLE_X86_HOST_DEBUG=True -DENABLE_INTERPRETER=False -DBUILD_TESTS=False -DENABLE_JEMALLOC=False -DENABLE_JEMALLOC_GLIBC_ALLOC=False -DENABLE_LLD=False -DCMAKE_INSTALL_PREFIX=${{runner.workspace}}/build/install
+
+    - name: Build
+      working-directory: ${{runner.workspace}}/build
+      shell: bash
+      # Execute the build.  You can specify a specific target with "--target <NAME>"
+      run: cmake --build . --config $BUILD_TYPE
+
+    - name: Set runner name
+      if: ${{ always() }}
+      run: echo "runner_name=$(hostname)" >> $GITHUB_ENV
+
+    - name: Upload results
+      if: ${{ always() }}
+      uses: 'actions/upload-artifact@v3'
+      timeout-minutes: 1
+      with:
+        name: Results-${{ env.runner_name }}
+        path: ${{runner.workspace}}/build/Testing/Temporary/LastTest_*.log
+        retention-days: 3
+