[Bug target/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 #15 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
Maybe I'm just thick, but from the generated
x86_64-apple-darwin17.0.0/libstdc++-v3/include/Makefile, it is entirely unclear
to me how the stamp mechanism and the current install-headers insures that
install-headers has completed in its entirety.  

The way I read the current Makefile is that it is merely checking for the
existence of the include subdirectories having been installed and not that that
they have been completely populated. Looks like a broken implementation of
stamps to me.