binutils/binutils: fix extra config array variable name

The changeset 2467 #200836977ce6 missed renaming one occurrence of
CT_BINUTILS_EXTRA_CONFIG to CT_BINUTILS_EXTRA_CONFIG_ARRAY, which is fixed by
this patch.

Signed-off-by: "Benoît Thébaudeau" <benoit.thebaudeau@advansee.com>
(transplanted from 8946dd980d9e6c3da3b8f63fe7e35f4af94acf2f)

# Compute Alpha-specific values

CT_DoArchTupleValues () {

    # The architecture part of the tuple:

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

}