make gnumach.gz: relocatable linking with relocations from format elf64-x86-64 to format elf32-i386 is not supported

[Paul Dufresne]

Trying to build Mach on Ubuntu 20.10.

I had a problem:
From: https://www.gnu.org/software/hurd/microkernel/mach/gnumach/building.html
I was doing: CPP='gcc -m32 -E -x c -undef -ansi' CC='gcc -m32' LD='ld 
-melf_i386' ../configure --prefix= --host=i686-unknown-linux-gnu
configure: error: in `/home/paul/mymach/gnumach/build':
configure: error: C compiler cannot create executables
See `config.log' for more details

I fixed it with: sudo apt install gcc-multilib

Also, after building mig: I was adding ~/bin to my PATH where ~/bin/mig was a 
symlink to ~/gnu/bin/mig ... as suggested in the doc...
that was not working, as it search ../libexec/migcom from ~/bin rather than 
from ~/gnu/bin ... note ~/gnu/libexec/migcom exist
So now I add to the PATH: ~/gnu/bin

Now my current problem is:
paul@jacko:~/mymach/gnumach/build$ LANG=C make gnumach.gz
ld -melf_i386  -u _start -r -o gnumach.o  libkernel.a liblinux.a 
liblinux_pcmcia_cs_modules.a liblinux_pcmcia_cs_clients.a 
liblinux_pcmcia_cs_wireless.a 
ld: relocatable linking with relocations from format elf64-x86-64 
(libkernel.a(model_dep.o)) to format elf32-i386 (gnumach.o) is not supported
make: *** [Makefile:4813: gnumach.o] Error 1

I begin to think I should build Mach on GNU Hurd/Mach.