To deal with fools^Wpeople trying to keep really old systems alive, create a proper framework for substitution functions, and make it possible to deal with the lack of snprintf/vsnprintf in particular.
For the canned makefiles, we almost certainly don't have config.h, and shouldn't include it in the list of dependencies.
Add a Makefile (for GNU Make, not wmake) to cross-compile NASM for DOS, OS/2 or Win32 using OpenWatcom.
