[Oberon] Compiling Original Oberon in (Unix)Aos?

[jwr at robrts.net]

At http://lists.inf.ethz.ch/pipermail/oberon/2016/008795.html Günter  
Feldmann wrote in answer to Eric Scharff:
    in the long period form 1989 to today the Oberon language as well
    as the object file format got some improvements. Some of them are
    incompatible. Therefore the old compiler and builder in the
    Oberon subsystem don't work any more, but they have to stay as
    parts of the old compiler get imported by modules belonging to
    other parts of the system.

    You can compile your module with the compiler in Aos and then
    start it in the Oberon subsystem.

Please help me understand, I think I misunderstand something critical.  
It sounds to me like this (UnixAOS) distribution is partially  
"broken", in that it is currently in a state different than it would  
be if everything was recompiled from source. Some objects currently  
exist with incompatible object-code formats?! Also it sounds like  
certain source files are written in different (incompatible?)  
"dialects" of the Oberon language. This suggests there is a  
significant possibility that right now the release cannot be  
completely recompiled successfully.

Recognizing that there is a chicken-and-egg problem regarding  
bootstrapping the compiler(s) [whose solution is well known and  
documented], are the proper procedures documented and available for  
cleanly recompiling everything in UnixAOS from scratch? Has anyone  
recently verified the procedures work properly? Is that useful/Does  
anyone care?

Theoretically there should be a file within the distribution which  
describes the exact procedure (with the proper commands listed) to  
recompile everything cleanly and properly. Perhaps not everything  
should be compiled with the same compiler: there may be a set of files  
compiled by the AOS compiler, another set by Oberon compiler #1, and  
yet another set by Oberon compiler #2, but it should somewhere be very  
clear exactly what to do.

-- John Roberts