Okay, so I've got a handlist of errors.
What I did was I took the offending makefiles from the vanilla compile and substituted. The offending makefiles are "dasm.make" and "skeleton.make".
I did a diff of the files, and dasm.make refers to objects that aren't in the vanilla build:
So if you replace "6x09dasm.o" with "6309dasm.o", "6809dasm.o", and "knmidasm.o", you get a valid makefile. This carries over to subsequent lines and references.
Then skeleton.make busts with the following references:
So the solution for skeleton.make was to get rid of the reference to "hazeltin.o"
This leads to an error win osd_winui.make, for which there is no vanilla substitute. The offending reference is:
make: *** [osd_winui.make:1605: ../../../../mingw-gcc/obj/x64/Release/osd_winui/src/osd/winui/mui_opts.o] Error 1
make: *** Waiting for unfinished jobs....
make: *** [Makefile:19: osd_winui] Error 2
make: *** [makefile:951: windows_x64] Error 2
Removing reference to "mui_opts.o" results in errors on linking, of course.
So something is wrong with dasm.make and skeleton.make, and this is breaking osd_winui.make.
Vanilla mame generates valid makefiles.
I don't know how to attach multiple files with this BBS, but I have all the files and errors documented. I'd be happy to share them.