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

[rlcamp.pdx at gmail dot com]

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

--- Comment #49 from Campbell <rlcamp.pdx at gmail dot com> ---
I can confirm that the latest gcc 8 snapshot still fails by default, but it
works with 8 cores using Chris's fix above of replacing ln -s with cp. This in
my mind pretty conclusively points to it not being a makefile logic error, but
rather a filesystem error. However, regardless of whose fault it is, Chris's
patch represents an actual viable solution to the problem, and is simple to
understand, and does not unduly penalize other platforms. This situation has
persisted for far too long and it makes GCC look bad and lose actual users,
regardless of whether Apple or GCC caused the problem.