At the place I worked in the early '80s [1], which did some games for Mattel for a couple 6502-based systems (Atari 2600 and Commodore VIC-20), we used small PDP-11s running some DEC operating system (I don't remember which one), using in-house written 6502 cross development tools. Each developer had a PDP-11.
Same setup for developing for game systems we worked with that used processors other than the 6502, such as the GI 1610 that was used in the Mattel Intellivision and the next generation successor to the Intellivision we were designing for Mattel.
We're talking old school here--as in you started your work day by toggling in a short boot loader via the front panel switches to get your computer going.
[1] https://en.wikipedia.org/wiki/APh_Technological_Consulting