[Bug target/104208] -mlong-double-64 should override a previous -mabi=ibmlongdouble

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104208

--- Comment #13 from Florian Weimer <fw at gcc dot gnu.org> ---
Thanks, I can confirm that we can build the glibc test suite once more in
Fedora rawhide.

(Fedora only needs the GCC 12 fix, it's our first GCC version with the float128
default).