Split Ruby CI into multiple parallel jobs

Run format, compile and db upgrade checks in parallel, along with the
main tests, which run in two parallel halves.

.github/workflows/ruby-qltest.yml

@@ -24,27 +24,45 @@ defaults:
     working-directory: ruby
 
 jobs:
-  qltest:
+  qlformat:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: ./.github/actions/fetch-codeql
-      - uses: ./ruby/actions/create-extractor-pack
-      - name: Run QL tests
-        run: |
-          codeql test run --threads=0 --ram 5000 --search-path "${{ github.workspace }}/ruby/extractor-pack" --check-databases --check-unused-labels --check-repeated-labels --check-redefined-labels --check-use-before-definition --consistency-queries ql/consistency-queries ql/test
-        env:
-          GITHUB_TOKEN: ${{ github.token }}
       - name: Check QL formatting
         run: find ql "(" -name "*.ql" -or -name "*.qll" ")" -print0 | xargs -0 codeql query format --check-only
+  qlcompile:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./.github/actions/fetch-codeql
       - name: Check QL compilation
         run: |
           codeql query compile --check-only --threads=0 --ram 5000 --warnings=error "ql/src" "ql/examples"
         env:
           GITHUB_TOKEN: ${{ github.token }}
+  qlupgrade:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./.github/actions/fetch-codeql
       - name: Check DB upgrade scripts
         run: |
           echo >empty.trap
           codeql dataset import -S ql/lib/upgrades/initial/ruby.dbscheme testdb empty.trap
           codeql dataset upgrade testdb --additional-packs ql/lib
           diff -q testdb/ruby.dbscheme ql/lib/ruby.dbscheme
+  qltest:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        slice: ["1/2", "2/2"]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./.github/actions/fetch-codeql
+      - uses: ./ruby/actions/create-extractor-pack
+      - name: Run QL tests
+        run: |
+          codeql test run --threads=0 --ram 5000 --slice ${{ matrix.slice }} --search-path "${{ github.workspace }}/ruby/extractor-pack" --check-databases --check-unused-labels --check-repeated-labels --check-redefined-labels --check-use-before-definition --consistency-queries ql/consistency-queries ql/test
+        env:
+          GITHUB_TOKEN: ${{ github.token }}