Using Snoopium I managed to avoid "cannot open -lamiga" problem. I
renamed amiga.lib from OS3.9 SDK to libamiga.a and copied to
GG:m68k-amigaos/lib.

Then I needed some inlines. First one for muimaster.library. I
generated it with fd2pragma from Aminet. After that GCC started
complain about macros inline. There was a problem, because there is a
clib/macros.h in OS3.9 SDK, but not fd/macros_lib.fd. Luckily I've
found needed inline (and many others, which I copied to my inline
directory) in this archive:
http://it.aminet.net/dev/gcc/fd2inline-bin.lha

Now I have different problem while linking. With MOS binutils version
I've got:
/gg/m68k-amigaos/bin/ld: BFD 2.13.1 internal error, aborting at ../../binutils-2.13.1/bfd/amigaoslink.c line 259 in get_relocated_section_contents
/gg/m68k-amigaos/bin/ld: Please report this bug.
collect2: ld returned 1 exit status

and for m68k version it is:
ld terminated with signal 6

Any ideas?...