libc/glibc: LinuxThreads are no longer supported in latest versions

In fact, it is only supported in a few legacy versions.

Keep LT available for all eglibc versions, although it might need
a similar safeguard...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Compute Alpha-specific values

CT_DoArchTupleValues () {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

}