[Bug libstdc++/81797] gcc 7.1.0 fails to build on macOS 10.13 (High Sierra):

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81797

--- Comment #51 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The patch in comment 45 is not acceptable for all platforms.

I'll entertain a patch that only affects the broken platforms, but not
something that will end up being carried around forever and for platforms with
working filesystems.