script/addToolsVersion: fix eglibc version separator

eglibc uses '_', not '.' to separate major/minor.

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

 reporter_name="Ioannis E. Venetis"

 reporter_url="http://sourceware.org/ml/crossgcc/2011-05/msg00005.html"

 reporter_comment=""