busybox

From Rich Paul:

I've noticed that when I compile busybox on my laptop, it compiles more
slowly than one would expect, and although it's a (more-or-less)
multiprocessor system and I use -j5, make never seems to run more than 
one job at a time.

I believe I have found the culprit:  each time a file is compiled, gcc
runs about 5 times.  This is because the $(check_gcc) macros and the
TARGET_ARCH macros are late binding.

The attached patch cuts the compilation time by 66%, from 1.5 minutes to
30 seconds.  Your mileage may very.  These statements have not been
evaluated by the FDA.