Borland C++, Microsoft C/C++, and GCC (DJGPP[1]) could all target 32-bit extended DOS, but Watcom was the first[2] to bundle a royalty-free DOS extender[3].
[1] https://news.ycombinator.com/item?id=39038095
[2] https://www.os2museum.com/wp/watcom-win386/
[3] https://en.wikipedia.org/wiki/DOS_extender