Question - looking at the code quickly, I see stuff about MWCC and Metrowerks object file format - is your tool chain in some way generating Metwowerks compatible object files? BeOS PowerPC uses the same compiler so you got me excited!
Yes and no. The MacRelix toolchain does, in a very trivial sense, generate Metrowerks-compatible object files, because mwcc is ultimately a wrapper around the Metrowerks-proprietary MWC68K and MWCPPC tools that run in MPW.
I reverse-engineered enough of the .o header format so that MacRelix's ar and ld could retrieve architecture and runtime information from a static library instead of making the caller provide it via a switch.
Separately, I've been writing post-linkers that patch or rewrite the Metrowerks-provided startup code in 68K code resources. The next step on this path might be writing my own compatible linker.
I'll come find you on Github, but I'd certainly be interested in getting involved in a Metrowerks compatible linker. The BeOS toolchain suffers from being so old that nothing modern compiles anymore and so this combined with other projects might make a replacement more viable. Because BeOS PowerPC uses PEF as the linker and a load of the support code is in the form of object code (they pretend to be static libs, but they are just object files) and as the API is in C++ and uses whatever the MW standard mangling was, replacing the linker without the object file format is not really viable.
https://www.metamage.com/text/relix/origins.html
I still use MPW's ToolServer for running the Metrowerks build tools, but sadly it's no longer available as an official download from Apple.