[Bug target/91349] [9 regression] powerpc*-*-freebsd* defines _GNU_SOURCE

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91349

--- Comment #9 from Alan Modra <amodra at gmail dot com> ---
> I have no idea which parts are GNU-specific, and which parts power actually needs.
Yeah, I was being cheeky in suggesting you provide the effort needed.

> I can just see that your change to include gnu-user.h on non-GNU targets seems like a design smell, and the requirement to kluge around it by #undef'ing things later confirms it.
If #undefs are a measure of "design smell" then rs6000/freebsd64.h already had
forty before I added two more.  Many of those are there due to including other
headers that define OS specific macros unsuitable for freebsd.

The mess is mostly due to rs6000/sysv4.h -mcall-<other-os> support.  Without
that I may not have needed to include gnu-user.h before rs6000/sysv4.h
everywhere.  The -mcall stuff needs to disappear before any meaningful
untangling of OS-specific macros in the rs6000 header files can be done.