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

["misty at brew dot sh" <gcc-bugzilla at gcc dot gnu dot org>]

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

Misty De Meo <misty at brew dot sh> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |misty at brew dot sh

--- Comment #3 from Misty De Meo <misty at brew dot sh> ---
I'm seeing a similar failure, also on macOS 10.13. I can only reproduce when
macOS is installed on an APFS filesystem, not HFS+. The issue occurs
intermittently, and the specific header that libstdc++ fails to find varies
from run to run.

/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/./gcc/xgcc
-shared-libgcc -B/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/./gcc
-nostdinc++
-L/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/src
-L/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/src/.libs
-L/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/libsupc++/.libs
-B/usr/local/Cellar/gcc/7.2.0/x86_64-apple-darwin17.0.0/bin/
-B/usr/local/Cellar/gcc/7.2.0/x86_64-apple-darwin17.0.0/lib/ -isystem
/usr/local/Cellar/gcc/7.2.0/x86_64-apple-darwin17.0.0/include -isystem
/usr/local/Cellar/gcc/7.2.0/x86_64-apple-darwin17.0.0/sys-include    -x
c++-header -nostdinc++ -g -O2 
-I/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include/x86_64-apple-darwin17.0.0
-I/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include
-I/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/libstdc++-v3/libsupc++  -O2
-g
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/libstdc++-v3/include/precompiled/stdc++.h
-o x86_64-apple-darwin17.0.0/bits/stdc++.h.gch/O2g.gch
In file included from
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include/sstream:38:0,
                 from
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include/complex:45,
                 from
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include/ccomplex:39,
                 from
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/libstdc++-v3/include/precompiled/stdc++.h:52:
/private/tmp/gcc-20170815-16334-85805x/gcc-7.2.0/build/x86_64-apple-darwin17.0.0/libstdc++-v3/include/istream:38:10:
fatal error: ios: No such file or directory
 #include <ios>
          ^~~~~

I can confirm that $target/libstdc++-v3/include/ios exists.