> In theory it should only be about writing a new build script (not based on `wmake` but on a real `make`). And then workout the tiny flag/preprocessor/C compiler discrepancies.
For mostly C code like the original Doom source, yes. But it looks like FastDoom people have added quite a bit of assembly. That needs to be ported to AT&T syntax. Or you need to find out if Intel syntax works in your version of DJGPP's gas. While this should work nowadays I have not tried it. Then there's other differences like Watcom mapping low memory by default into the low part of the address space but DJGPP needing explicit mapping or access.
For mostly C code like the original Doom source, yes. But it looks like FastDoom people have added quite a bit of assembly. That needs to be ported to AT&T syntax. Or you need to find out if Intel syntax works in your version of DJGPP's gas. While this should work nowadays I have not tried it. Then there's other differences like Watcom mapping low memory by default into the low part of the address space but DJGPP needing explicit mapping or access.