XLF: enable builds with XLF + Ninja generator
Fixes #19450 (closed)
- add support for CMake builds with the XLF compiler using the "Ninja" generator; this is accomplished by adding a custom preprocessor line for XLF that handles its idiosyncrasies
So far, tested locally with a large mixed C/C++/Fortran code base to successfully build/link the project with XL toolchain.