debug/tools: set the ncurses extension to .tar.gz

TRying to download every extension in turn takes ages, so
help the helper by telling what extension to retrieve.
(transplanted from 08b0982e4da9402ad39fde431353ebf0248ea34c)

 reporter_name="Yann E. MORIN"

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

 reporter_comment=""