IPO: -f[no-]fat-lto-objects are not cross-platform GCC options
With CMake 3.29.2, the Compiler/GNU.cmake module will add -fno-fat-lto-objects
and Compiler/FortranCInterface/CMakeLists.txt will add -ffat-lto-objects
unconditionally when using a GNU compiler.
AFAIK those are only supported with ELF objects and indeed the former causes compiler failures when activating interprocedural optimisation using GCC on Mac. Easy to fix by adding AND NOT APPLE
to the condition.
I strongly suspect that LTO will simply have to be avoided on APPLE in the latter file.