[build2] build w gcc 8.1.1 + c++1y fails

[Boris Kolpackov]

MM <finjulhich at gmail.com> writes:

> g++ -I../libbutl -DLIBBUTL_STATIC -I../libpkgconf -DPKGCONFIG_IS_STATIC -I.
> -std=c++2a -MQ ^ -x c++ -MD -E -fdirectives-only -MF build2/config/init.o.t
> -o /tmp/init.o.ii build2/config/init.cxx

Thanks! We've tried to compile it with "g++ (GCC) 8.1.1 20180502 (Red Hat
8.1.1-1)" which is the closest to yours we could find. No errors. So it
looks like a fairly recent regression in GCC. Before I file a bug report,
can you confirm that this produces the error for you:

g++ -DLIBBUTL_STATIC -DPKGCONFIG_IS_STATIC -std=c++2a -o init.o -c -fdirectives-only init.o.ii