CI: install pip with fix for isolated build environment on Debian

Author: dnicolodi

.cirrus.yml

@@ -2,6 +2,8 @@ test_template: &test
   test_script:
     - command -v python3
     - python3 --version
+    # Install pip with fix isolated build environments on Debian
+    - python3 -m pip install --upgrade "pip @ https://github.com/pypa/pip.git@refs/pull/11623/merge"
     - python3 -m pip install .[test]
     - python3 -m pytest