cc/gcc: fix linking with static PPL 0.11+

PPL 0.11+ installs three libs: lippl, libppl_c and libpwl.
libppl_c has a dependency on libpwl (at least for watchdog stuff).

While gcc correctly links with libppl and libppl_c, it does not
pull libpwl in. In case of shared libs, this is not a problem, as
libppl_c has a NEEDED dependency on libpwl. But for static libs,
that does not work. Although libppl_c.la exists and has a correct
dependency on lipwl, somehow gcc misses it. So we have to force
pulling libpwl when needed.

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

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