First, thanks for excellent explanation, as always. Google will remember you ;-)
You're damned because Linux people don't care about things other than ELF. However, xBSD still use a.out and the same issues would appear.
Actually, this is quite easy problem, I just disable -nostdlib in configure script. What is worse, this library tries to be really smart and check for all variants gcc is able to provide (mshort, mshort/m68020-60, ...) and guess what -- libc.a is missing and thefore also stuff referenced in crt0.o like __basepage. I must use standard libs but I can't use it for -mshort which raises my original problem. Amazing. I think I finally disable all that -mshort crap in gcc, I don't care about 68000 XaAES, what is last remaining piece of software requiring -mshort libgcc :-/