Add PR check job for Ruby beta

Add a separate job that analyses the multilanguage test repo's Ruby code.
For now, run this only with the latest nightly build of CodeQL,
since the latest released build and the cached builds don't support Ruby yet.

In future when the latest released build supports Ruby,
we can update this and other PR checks to test a wider range of cases.

Author: adityasharad

.github/workflows/pr-checks.yml

@@ -497,6 +497,47 @@ jobs:
           exit 1
         fi
 
+  # Ruby is in beta, so test it separately for now.
+  multi-language-repo_test-ruby:
+    needs: [check-js, check-node-modules, check-codeql-versions]
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        tools:
+          # TODO: Add `latest` here when `defaults.json` points to
+          # a CodeQL release that supports Ruby in beta.
+          - ${{ needs.check-codeql-versions.outputs.nightly-url }}
+    runs-on: ${{ matrix.os }}
+    env:
+      CODEQL_ENABLE_EXPERIMENTAL_FEATURES: true
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Move codeql-action
+      shell: bash
+      run: |
+        mkdir ../action
+        mv * .github ../action/
+        mv ../action/tests/multi-language-repo/{*,.github} .
+        mv ../action/.github/workflows .github
+    - uses: ./../action/init
+      with:
+        languages: ruby
+        tools: ${{ matrix.tools }}
+    - uses: ./../action/analyze
+      id: analysis
+      env:
+        TEST_MODE: true
+    - name: Check database
+      shell: bash
+      run: |
+        RUBY_DB="${{ fromJson(steps.analysis.outputs.db-locations).ruby }}"
+        if [[ ! -d "$RUBY_DB" ]]; then
+          echo "Did not create a database for Ruby."
+          exit 1
+        fi
+
   multi-language-repo_rubocop:
     needs: [check-js, check-node-modules]
     runs-on: ubuntu-latest

tests/multi-language-repo/.github/codeql/custom-queries.yml

@@ -1,3 +1,4 @@
+
 name: Use custom queries
 
 disable-default-queries: true