There's no need to set the default for GNUCXX based on WITHOUT_CXX
being defined. The system works fine without it (because GNUCXX isn't
built when WITHOUT_CXX is defined), and it is one of the few places we
test WITHOUT_FOO instead of MK_FOO in the base system. Simply
eliminate it to solve both problems. Also, minor tweak to make it
clearer that the default is always NO for GNUGCC on i386.