cc/gcc: with static ppl, correctly link with libm

On some Fedora boxen (at least FC13), it is also required
to link with libm when static ppl is used.
(transplanted from bcd33fce4db9c18223b59ecdc96f10bf6dd574de)

 reporter_name="Bart vdr. Meulen <bartvdrmeulen@gmail.com>"

 reporter_url=""

 reporter_comment="Config to build cross-compiler with mingw as kernel type"