does not cross compile due to wiringpi makefile setup

wiring-pi does not crosscompile; the problem is that wiringpi hardcodes CC=gcc in its makefiles, so the wiringpi bits get always built with the host compiler. A possible solution is to add another patch that fixes that assingment to 'CC ?= gcc' and then set CC in the environment (i.e., install.sh) to point at CC.target.
