[Bug libstdc++/108630] build failure with LTO enabled

[a.heider at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108630

--- Comment #1 from Andre Heider <a.heider at gmail dot com> ---
Forgot to mention:
CXXFLAGS_FOR_TARGET="$CFLAGS_FOR_TARGET"

Obviously :)