[Bug bootstrap/70704] [6 Regression] AIX bootstrap comparison failure

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70704

--- Comment #45 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't think M4 env var should make a difference in this case, in the release
tarballs the gengtype-lex.c file is already built (on x86_64-linux) and nothing
should be changing that.

That said, I've managed to reproduce the miscompare on build/ggc-none.o as an
example of very small source file, even with -g0.  But it looks really weird.
First of all, it seems that the system g++ 4.8 and g++ 6.1-rc2 is probably ABI
incompatible, at least my attempts to mix stage1 and stage2 objects into the
same binary failed miserably.  I've rebuilt stage2-gcc/ cc1plus with
CXXFLAGS='-g -O0', thus most if not all *.o files linked into it should be
(like in stage1) built without optimizations, and still see the differences.
Trying to find out where the differences start now using parallel gdb sessions.