Fix the options when compiling under OpenWatcom

Fix the options when compiling under OpenWatcom

OpenWatcom needs different strings for compile and link target, so
using -bcl which uses the same string for both is just plain wrong.
This fixes that bit, but running nasm on test/floatx.asm (at least as
a DOS or a Win32 binary) crashes with a NULL pointer reference inside
the C library free() function.