Don't recompile everything when one mib file changes
Don't recompile everything when one mib file changes

Fixes a bug detected with the test introduced in the previous commit.

bsmr-erlang/erlang.mk,ingwinlu/erlang.mk,hairyhum/erlang.mk,jj1bdx/erlang.mk,rabbitmq/erlang.mk,a12n/erlang.mk,nevar/erlang.mk,KrzysiekJ/erlang.mk,crownedgrouse/erlang.mk,ninenines/erlang.mk