configure: check for GNU awk, not any awk

Building glibc requires GNU awk, not any other.

Reported-by: Han Sooloo <hansooloo@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # Compute M68k-specific values

 CT_DoArchTupleValues() {

     :

 }