scripts: do not chmod u+w the whole source directory

Doing a chmod on the whole source dir after every packages
are extracted can take a hell of a lot of time.

The offending packages are far from legion, and they now
have their own chmod u+w to cleanup their own mess...

Reported-by: ANDY KENNEDY <ANDY.KENNEDY@adtran.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

reporter_name="Thomas Petazzoni"

reporter_url="http://www.free-electrons.com/"

reporter_comment="Very basic testing only"