Swift: run QL tests on macOS

.github/actions/fetch-codeql/action.yml

@@ -3,12 +3,22 @@ description: Fetches the latest version of CodeQL
 runs:
   using: composite
   steps:
+    - name: Select platform - Linux
+      if: runner.os == 'Linux'
+      shell: bash
+      run: echo "GA_CODEQL_CLI_PLATFORM=linux64" >> $GITHUB_ENV
+
+    - name: Select platform - MacOS
+      if: runner.os == 'MacOS'
+      shell: bash
+      run: echo "GA_CODEQL_CLI_PLATFORM=osx64" >> $GITHUB_ENV
+
     - name: Fetch CodeQL
       shell: bash
       run: |
         LATEST=$(gh release list --repo https://github.com/github/codeql-cli-binaries | cut -f 1 | grep -v beta | sort --version-sort | tail -1)
-        gh release download --repo https://github.com/github/codeql-cli-binaries --pattern codeql-linux64.zip "$LATEST"
-        unzip -q -d "${RUNNER_TEMP}" codeql-linux64.zip
+        gh release download --repo https://github.com/github/codeql-cli-binaries --pattern codeql-$GA_CODEQL_CLI_PLATFORM.zip "$LATEST"
+        unzip -q -d "${RUNNER_TEMP}" codeql-$GA_CODEQL_CLI_PLATFORM.zip
         echo "${RUNNER_TEMP}/codeql" >> "${GITHUB_PATH}"
       env:
         GITHUB_TOKEN: ${{ github.token }}

.github/workflows/swift-qltest.yml

@@ -20,19 +20,26 @@ jobs:
       - name: Check QL formatting
         run: find ql "(" -name "*.ql" -or -name "*.qll" ")" -print0 | xargs -0 codeql query format --check-only
   qltest:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
+      matrix:
+        os : [ubuntu-20.04, macos-latest]
     steps:
       - uses: actions/checkout@v2
       - uses: ./.github/actions/fetch-codeql
-      - name: Install bazelisk
+      - name: Install bazelisk - Linux
+        if: runner.os == 'Linux'
         run: |
           sudo apt-get update
           sudo apt-get install -y wget
           wget https://github.com/bazelbuild/bazelisk/releases/download/v1.11.0/bazelisk-linux-amd64
           mv bazelisk-linux-amd64 /usr/local/bin/bazel
           chmod +x /usr/local/bin/bazel
+      - name: Install bazelisk - macOS
+        if: runner.os == 'MacOS'
+        run: |
+          brew install bazelisk
       - name: Build Swift extractor
         run: |
           bazel run //swift:create-extractor-pack
@@ -41,3 +48,4 @@ jobs:
           codeql test run --threads=0 --ram 5000 --search-path "${{ github.workspace }}/swift/extractor-pack" --check-databases --check-unused-labels --check-repeated-labels --check-redefined-labels --check-use-before-definition ql/test
         env:
           GITHUB_TOKEN: ${{ github.token }}
+