Windows CI for Ray on github actions (#6519)

* Windows CI for Ray

* Update main.yml

* Does this work?

* Download Bazel to current directory

* Install required packages via Chocolatey

* Improve the Windows CI script

.github/workflows/main.yml

@@ -0,0 +1,97 @@
+name: CI
+
+on: [push]
+
+jobs:
+  build:
+    name: ${{ matrix.name }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        # Github Actions requires a single row to be added to the build matrix.
+        # See https://help.github.com/en/articles/workflow-syntax-for-github-actions.
+        name: [
+          windows-clang-cl,
+        ]
+        include:
+          - name: windows-clang-cl
+            os: windows-latest
+            compiler: clang-cl
+    steps:
+    - name: Install Bazel
+      shell: bash
+      run: |
+        if [ "${OSTYPE}" = "msys" ]; then
+          choco install --no-progress bazel
+        fi
+    - name: Install C/C++ toolchains
+      if: matrix.compiler == 'clang' || matrix.compiler == 'clang-cl'
+      shell: bash
+      run: |
+        if [ "${OSTYPE}" = "msys" ]; then
+          choco install --no-progress llvm
+        elif 1>&- command -v pacman; then
+          sudo pacman -S --needed --noconfirm --noprogressbar clang
+        elif 1>&- command -v apt-get; then
+          sudo apt-get -q -y install clang
+        fi
+    - name: Install MSYS2 (only needed if some shell commands are missing)
+      if: false && runner.os == 'Windows'
+      uses: numworks/setup-msys2@v1
+      with:
+        update: false
+    - name: Checkout repository
+      uses: actions/checkout@v1
+      with:
+        fetch-depth: 1
+    - name: Perform build
+      shell: bash
+      run: |
+        set -euo pipefail
+        main() {
+          if [ "${OSTYPE}" = "msys" ]; then
+            export MSYS2_ARG_CONV_EXCL="*"  # Don't let MSYS2 attempt to auto-translate arguments that look like paths
+            local latest_python_bin=""
+            for latest_python_bin in /proc/registry/HKEY_LOCAL_MACHINE/Software/Python/PythonCore/*/InstallPath/@; do
+              if [ -f "${latest_python_bin}" ]; then
+                latest_python_bin="$(tr -d '\0' < "${latest_python_bin}")"
+                latest_python_bin="${latest_python_bin}\\"
+              else
+                latest_python_bin=""
+              fi
+            done
+            latest_python_bin="${latest_python_bin}python.exe"
+            if [ -f "${latest_python_bin}" ]; then
+              export PYTHON2_BIN_PATH="${latest_python_bin}" PYTHON3_BIN_PATH="${latest_python_bin}"
+            fi
+          fi
+          # NOTE: Only options that are _user preferences_ (i.e. not repository-specific) should go here.
+          # These are options that people may disagree on having on their own machines, but which are useful for our builds.
+          bazel_output_root="${HOME}/bazel"
+          if [ "${OSTYPE}" = "msys" ]; then
+            bazel_output_root="$(cygpath -w -- "${bazel_output_root}")"
+          fi
+          local startflags=()
+          startflags+=(--batch)
+          startflags+=(--nodeep_execroot)
+          #startflags+=(--output_user_root="${bazel_output_root}")
+          local cmdflags=()
+          cmdflags+=(--attempt_to_print_relative_paths)
+          cmdflags+=(--color=yes)
+          cmdflags+=(--experimental_repository_cache_hardlinks)
+          cmdflags+=(--experimental_ui_deduplicate)
+          cmdflags+=(--incompatible_strict_action_env)
+          cmdflags+=(--keep_going)
+          cmdflags+=(--per_file_copt="-\\.(asm|S)$@-fansi-escape-codes")
+          cmdflags+=(--per_file_copt="-\\.(asm|S)$@-fcolor-diagnostics")
+          cmdflags+=(--show_progress_rate_limit=5)
+          cmdflags+=(--show_task_finish)
+          cmdflags+=(--show_timestamps)
+          cmdflags+=(--symlink_prefix=/)
+          cmdflags+=(--verbose_failures)
+          local packages=()
+          packages+=("//:ray_pkg")
+          bazel "${startflags[@]}" build "${cmdflags[@]}" "${packages[@]}" "$@"
+        }
+        main "$@"