powerpc64le: guarantee a .gnu.attributes section [BZ #26220]
Upstream GCC 11 development is now building the ibm128 runtime
support (in libgcc) without a .gnu.attributes section on ppc64le.
Ensure we have one to replace by building one ibm128 file in
libc and libm with attributes.
Reviewed-by: Carlos O'Donell <carlos@redhat.com> Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>