scripts/functions: properly catch failure in CT_Test* helpers

So we get caught by the trap-handler and
have a chance to run the debug-shell.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Johannes Stezenbach <js@sig21.net>

 reporter_name="Alexander BIGGA"

 reporter_url="http://sourceware.org/ml/crossgcc/2008-06/msg00031.html"

 reporter_comment=""