A solution is to build a ColdFire-only GCC, without multilib.
This doesn't seem right. Imagine you are an Atari developer and happy user of FireBee -- how would you compile multiple versions of your software? OK, you could write always all paths explicitly (-L/usr/lib/m6802060) but that's definitely more annoying than adding simple '-m68020-60' and everything gets compiled and linked as it supposed to be.