libc/uclibc: fix src dir location

Now that we akways extract the tarballs in a sane location (see changeset
#6e1412ba8da9: scripts/functions: force extract folder to archive basename),
the uClibc snapshot dir now has the date (as version) in it, eg.:
uClibc-20100710

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

 reporter_name="Alexander BIGGA"

 reporter_url="http://sourceware.org/ml/crossgcc/2008-07/msg00000.html"

 reporter_comment=""