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>

 Index: ltrace-0.5.3/configure

 ===================================================================

 --- ltrace-0.5.3/configure

 +++ ltrace-0.5.3/configure

 @@ -78,7 +78,10 @@ fi

  rm -f conftest.c a.out

  CFLAGS='-g -O2'

 -LIBS='-lelf -lsupc++ -liberty '

 +LIBS='-lelf'

 +[ -n "$HAVE_LIBSUPC__" ] && LIBS="$LIBS -lsupc++"

 +[ -n "$HAVE_LIBIBERTY" ] && LIBS="$LIBS -liberty"

 +

  INSTALL='install -c'

  iquote='-iquote '

  iquoteend=''