Tools: install_prereqs_ubuntu.sh: pin setuptools to avoid problems on…

… Focal

    focal:     return Version(version)
    focal:   File "/home/vagrant/.local/lib/python3.8/site-packages/packaging/version.py", line 202, in __init__
    focal:     raise InvalidVersion(f"Invalid version: '{version}'")
    focal: packaging.version.InvalidVersion: Invalid version: '1.0.3.linux-x86_64'

Tools/environment_install/install-prereqs-ubuntu.sh

@@ -400,7 +400,11 @@ if [ -n "$PYTHON_VENV_PACKAGE" ]; then
 fi
 
 # try update packaging, setuptools and wheel before installing pip package that may need compilation
-$PIP install $PIP_USER_ARGUMENT -U pip packaging setuptools wheel
+SETUPTOOLS="setuptools"
+if [ ${RELEASE_CODENAME} == 'focal' ]; then
+    SETUPTOOLS=setuptools-70.3.0
+fi
+$PIP install $PIP_USER_ARGUMENT -U pip packaging $SETUPTOOLS wheel
 
 if [ "$GITHUB_ACTIONS" == "true" ]; then
     PIP_USER_ARGUMENT+=" --progress-bar off"