Install -dev libs for lxml for PyPY CI jobs.

Author: wRAR

.github/workflows/tests-ubuntu.yml

@@ -12,6 +12,12 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
+    - name: Install system libraries
+      if: contains(matrix.python-version, 'pypy')
+      run: |
+        sudo apt-get update
+        sudo apt-get install libxml2-dev libxslt-dev
+
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with: