As far as I understand it, the m68k LLVM port is not ABI-compatible with GCC on Linux because the alignment is wrong: https://wiki.debian.org/M68k/Alignment (page says that the LLVM packages are FTBFS because of this)
The principled way to address this would be to define a new ABI suffix for the m68k-unknown-linux-gnu target triple, replacing the existing 'gnu' which would retain GCC compatibility with 2-byte alignment for int.
