devel/llvm-devel: update to a fresh snapshot

This update includes a switch to a new layout for
runtime libraries. Rather than being stored in
llvm-devel/lib/clang/${LLVM_RELEASE}/lib/freebsd
with -<arch> suffixes, they are now stored in
llvm-devel/lib/clang/${LLVM_RELEASE}/lib/${CONFIGURE_TARGET}.
In principle, the compiler should just use the new locations
and this should be a no-op.