Ability to redefine *config-fn-symbol* in lein project

[iced]

Spent about hour or so, it looks impossible. It's impossible to use :global-vars - as it expands to set! which can't re-set dynamic and there is no other way to interfere.\

For some legacy purposes I need my migration config in src/migrations/config.clj (don't even ask). Symlink worked fine so far, but now I need to support windows as well ;)

Simple :drift-config option in lein plugin 'd be really helpfull.

[macourtney]

I will take a look at this when I get the chance.