One of the strengths of autosetup is that it doesn't rely on any tools other than a C compiler and make (at least from my readings of it). It uses Tcl-based scripts (a strict subset of Tcl), but it includes a Tcl interpreter (in source) that can execute that subset as part of the build process so there's no need for the host environment to supply one.
Given Fossil's goals of being usable, essentially, on any platform that has an ANSI-compliant C compiler (within reason), I think that its adoption of autosetup hints that Lua, with a similar goal, could probably easily do the same.
