Toolchain becomes package set part2

This is mostly a search and replace exercise (and thus probably correct). (Individual commits deal with kind-of single functions, and their associated tests.)

More complicated changes I have tried to move into separate merge requests.

tests.py

@@ -7,6 +7,7 @@ import subprocess
 from pathlib import Path
 import logging
 import datetime
+import sys
 
 import pytest
 
@@ -210,6 +211,7 @@ def test_install_environment_wrong_mpsd_release(tmp_path):
         )
 
 
+@pytest.mark.skipif(sys.platform == "darwin", reason="install not working on OSX")
 def test_install_environment_zlib():
     """Test installation of package_set."""
     # Prepare a test installation of global generic