To enable Flang testing on Windows,
shells scripts have to be ported to Python.
The following changes have been made:
Ported `test_folding.sh` to Python;
Additional changes to the tests themselves
to use the new script.
LIBPGMATH support for testing
not available at this point.
Reviewed By: Meinersbur
Differential Revision: https://reviews.llvm.org/D108217