ci: Add an ARM Linux test workflow

Like the macOS jobs are mixed between Intel and ARM, this changes one of
the Linux jobs to use ARM.

.github/workflows/tests.yml

@@ -78,7 +78,7 @@ jobs:
             # https://bugreports.qt.io/projects/PYSIDE/issues/PYSIDE-2346
             pyside6-ver: '!=6.5.1'
             extra-requirements: '-r requirements/testing/extra.txt'
-          - os: ubuntu-22.04
+          - os: ubuntu-22.04-arm
             python-version: '3.12'
             # https://www.riverbankcomputing.com/pipermail/pyqt/2023-November/045606.html
             pyqt6-ver: '!=6.6.0'
@@ -282,10 +282,13 @@ jobs:
               echo 'PyGObject 3 is available' || echo 'PyGObject 3 is not available'
             )
 
-          python -mpip install --upgrade pyqt5${{ matrix.pyqt5-ver }} &&
-            python -c 'import PyQt5.QtCore' &&
-            echo 'PyQt5 is available' ||
-            echo 'PyQt5 is not available'
+          # PyQt5 does not have any wheels for ARM on Linux.
+          if [[ "${{ matrix.os }}" != 'ubuntu-20.04-arm' ]]; then
+            python -mpip install --upgrade pyqt5${{ matrix.pyqt5-ver }} &&
+              python -c 'import PyQt5.QtCore' &&
+              echo 'PyQt5 is available' ||
+              echo 'PyQt5 is not available'
+          fi
           # Even though PySide2 wheels can be installed on Python 3.12+, they are broken and since PySide2 is
           # deprecated, they are unlikely to be fixed. For the same deprecation reason, there are no wheels
           # on M1 macOS, so don't bother there either.