Blargg's test ROM sources have references to the ability to build NSFs. It seems like at some point there were two files, nsf.cfg and build_nsf.s in the common folder, but none of the projects I could find include these.
I can try to build my own, but if anyone knows where these might be found I'd appreciate it.
Edit:
Here's my own attempt, seems to be working with instr_test-v3.zip (haven't tested much so far). I've added nsf.cfg and build_nsf.s, and there is one minor change to shell.s (changed .ifdef NEED_CONSOLE on line 162 to .if NEED_CONSOLE).
I can try to build my own, but if anyone knows where these might be found I'd appreciate it.
Edit:
Here's my own attempt, seems to be working with instr_test-v3.zip (haven't tested much so far). I've added nsf.cfg and build_nsf.s, and there is one minor change to shell.s (changed .ifdef NEED_CONSOLE on line 162 to .if NEED_CONSOLE).