[3.9] bpo-41116: Fix setup.py test for macOS Tcl/Tk frameworks (GH-23649) (GH-23650)

If no explicit macOS SDK was specified, setup.py should check for
Tcl and TK frameworks in /Library/Frameworks; the previous commit
inadvertently broke that test.
(cherry picked from commit 29afab6c5f656f07ac85c9b2cf089631b2557a11)

Co-authored-by: Ned Deily <nad@python.org>
2 files changed