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

[howarth.at.gcc at gmail dot com]

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

--- Comment #9 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
(In reply to Francois-Xavier Coudert from comment #8)
> Can reproduce with GNU Make 4.2.1, on the same system.

I assume all of these builds are done using a gcc7.rb file run under ruby,
correct? You might try a manual build outside of ruby (but duplicating there
exact build approach). 

There is a history of certain race condition bugs only being exposed when make
is run under a particular program...

http://savannah.gnu.org/bugs/index.php?46261