facility to generate "flavor" subdir like `get-directory-name subdir` in ups...
...so non-qualified ups products don't need to depend on cetpkgsupport.
I think "new" flavor support should be in ups. I.e. ups' old
flavor could be remain, but there should be a modern flavor facility
in UPS. Once this is done, cetbuildtools can use it and at when building
table files, at least for non-qualified products, can eliminate a dependence