[Bug libstdc++/47368] New: CFLAGS_FOR_TARGET, profiledbootstrap and lto-bootstrap flags unused in libstdc++-v3

[Jan Hubicka]

>    The  libstdc++-v3 build also doesn't utilize the profiling flags produced in
> a profiledbootstrap or the lto flags produced from an lto-bootstrap.
profiledbootstrap/lto-bootstrap is about FDO/LTO while building compiler, not runtime.
It would probably make sense for libstdc++-v3 to eventually build the shared lib with
LTO, but we need to solve debug info quality issues...

Honza