VBCC seems to rely on a pre-existing assign to include:

If you're using a 68k specific set of include files then you'll have to figure out where the assign to include: should point to.

I once tried to document my own solution to a similar problem...

http://library.morph.zone/An_Introduction_to_MorphOS_PPC_Assembly#MorphOS_SDK.2C_Objdump.2C_ELFs_.26_Sections