Use ICF linker optimization for other platforms than Linux

[Kobzol]

#99062 added ICF (identical code folding) for Linux builds of rustc, in order to slightly optimize binary size and i-cache utilization. It could be worthwhile to also investigate if we can apply it on other platforms. It could be also expanded to other compiler artifacts, like stdlib.

[workingjubilee]

This should not happen until we diagnose what happened here:

• rustup linux rustc executable not executable (symbol lookup error) #99440

[workingjubilee]

Given what happened in #99440 we're probably fine proceeding here, but should keep an eye peeled for more Hilarity.