libc/glibc: let glibc 3.3.6 link correctly

From http://sourceware.org/git/?p=glibc.git;a=commit;f=elf/Makefile;h=7c8a67320e26b8c11108bf0a3410d3aef9cf3486

Author: Ulrich Drepper <drepper@redhat.com>:
Commit log:
* elf/Makefile (ld.so): Adjust the sed script to insert _begin in to
newer linker scripts.

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>

# Compute s390-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

    if [ "${CT_ARCH_64}" = "y" ]; then

        CT_TARGET_ARCH="s390x"

    fi

}