sys-libs/glibc: Drop SPARC CHOST mangling

sys-libs/glibc: Drop SPARC CHOST mangling

Before "multiarch" support in glibc, picking a different CHOST would
select which optimized paths were built. Multiarch support was added in
glibc commit 3afd5a3b5556 (sparc: Add multiarch support for
memset/bzero/memcpy.) in 2010 before glibc-2.12.

Before glibc-2.30 glibc dropped support for SPARC v7 in commit
5d9b7b9fa734 (Remove 32 bit sparc v7 support) and in the process cleaned
up some configuration logic that accepted a wide variety of (now unused
CHOST values), thus causing the build to fail for us when we select a
now unknown CHOST.

Simply drop this logic, since it shouldn't be needed for any glibc since
2.11.

Signed-off-by: Matt Turner <mattst88@gentoo.org>