scripts/functions: do not abort on failed extract

For glibc/eglibc, if the add-on can not be extracted, we want to catch
the error to print a meaningful error message.

So:
- try to extract the tarball
- if it fails, print a waring instead of calling CT_Abort
- return 1

So, components that want to catch the error and want to handle it can,
while components that do not will gracefuly fail thanks to our catching
every errors.

Bonus: it works without changing any existing extract procedure! :-)

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

reporter_name="Yann E. MORIN"

reporter_url=""

reporter_comment="EXPERIMENTAL uClibc/NPTL snapshot."