Comment # 6 on bug 1204790 from Richard Biener

I see quite a bunch of packages BuildRequiring glibc-devel-32bit: carla,
dynamips, grub2, ispc, lsb, memtest86+, papi, qemu, vacation, valgrind and xen

In the past on ppc that resulted in glibc-devel-64bit to be pulled so
glibc-devel-32bit is magic for "the other multilib".

Then there's another set of packages requiring gcc-32bit which also pulls
glibc-devel-32bit (but gcc-32bit itself isn't magic).

So yes, I think we still need -m32 support.  Definitely for GCC development
itself.

Some of the above packages might also rely on the project config
replacing glibc-devel-32bit with nothing.

I think we might be able to replace the "hack" with

%if "%{bi}" != ""
BuildRequires: glibc-devel%{bi}
%endif

when %{bi} expands to -32bit, -64bit or %nil?

Most issues will probably be noticed in the mips and sparc builds where
main 32bit and 64bit multilib are still present.