These files are created by configure and grow
unnecessarily at each new call of configure:

roms/seabios/config.mak
roms/vgabios/config.mak
libhw32/config.mak
libhw64/config.mak

libhw32/config.mak and libhw64/config.mak set
compiler options, and the wrong old code results
in very long command lines.

The new code always writes a new config.mak
instead of appending to an existing one.
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>