Add a new job to build and test cross-builds in the JIT workflow

* **Cross-Build Job**
  - Add a new job named `Cross-Builds` to the JIT workflow
  - Checkout code using `actions/checkout@v2`
  - Set up Python using `actions/setup-python@v2`
  - Install build-essential dependencies
  - Build host Python and install it
  - Configure cross-build with the host Python
  - Run tests in the build directory
  - Install cross-build
  - Run tests with the installed Python

.github/workflows/jit.yml

@@ -167,3 +167,38 @@ jobs:
       - name: Run tests
         run: |
           ./python -m test --multiprocess 0 --timeout 4500 --verbose2 --verbose3
+
+  cross-build:
+    name: Cross-Builds
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.x'
+
+      - name: Install dependencies
+        run: sudo apt-get install -y build-essential
+
+      - name: Build host Python
+        run: |
+          ./configure --prefix=$PWD/workdir/host-python
+          make -j4
+          make install
+
+      - name: Configure cross-build
+        run: |
+          ./configure --with-build-python=$PWD/workdir/host-python/bin/python --prefix=$PWD/workdir/cross-python
+          make -j4
+
+      - name: Run tests in build directory
+        run: ./python -m test test_sysconfig test_site test_embed
+
+      - name: Install cross-build
+        run: make install
+
+      - name: Run tests with installed Python
+        run: $PWD/workdir/cross-python/bin/python -m test test_sysconfig test_site test_embed