Allows building the #mold linker, which can then be used in the
cross-toolchain by passing the -fuse-ld=mold to the gcc flags. It is
much faster than ld or gold.
This requires a C++20 compiler and cmake.
Initially implemented by Arnaud, and HC added configure check for cmake.
Outstanding task to validate compiler is C++20 compatible.
Signed-off-by: Arnaud Vrac <avrac@freebox.fr>
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
