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>

 reporter_name="YEM"

 reporter_url="http://ymorin.is-a-geek.org/"

 reporter_comment="EXPERIMENTAL Super-H sh4 sample."