File gcc-m-fpu.cmake is responsible for determining what should be
passed to -mfpu option. Fortunately GCC and Clang options are compatible
so we can use the file for clang.
The list of supported -mfpu options can be found at
https://github.com/llvm/llvm-project in
llvm/include/llvm/TargetParser/ARMTargetParser.def file.
Signed-off-by: Patryk Duda <pdk@semihalf.com>