FindMPI: backport from CMake 3.22
CMake < 3.20 woes?
See !8349 (merged).
Fixes issues with new MPICH on macOS where -framework
gets passed
around as a "free radical" compilation flag.
Also comes with Fujitsu, IntelLLVM, PGI, and Cray compiler fixes and CUDA device/host compilation fixes.
See: cmake/cmake#22555 (closed) See: cmake/cmake!6467 (merged)