On Windows NT building software from source under Interix[0] (nee OpenNT, later "Subsystem for Unix Applications") was pretty nice.

Interix was implemented as proper NT kernel "subsystem". It was just another build target for GNU automake, for example.

(Being that Interix was a real kernel subsystem I have this fever dream idea of a text-mode "distribution" of NT running w/o any Win32 subsystem.)

[0] https://en.wikipedia.org/wiki/Interix