The tests-if-CYGWIN topic made a change to Tests/Testing/CMakeLists.txt
in code that the custom-command-generator-expressions topic moved to the
Tests/PerConfig/CMakeLists.txt file. Make the same change to the same
content in the new file. (Only a small part of the file moved so rename
detection did not do this automatically.)
Put the source files, build rules, and test scripts for these targets
under Tests/PerConfig and refer to it from Tests/Testing as a
subdirectory. The targets and scripts will be useful in other tests.