complibs/ppl: build watchdog library

gcc-4.6+ requires the Parma Watchdog Library (libpwl).
Build it and use it.

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"