Fixing issue #126 with Leiningen 2.5.0 due to auto-cleaning of targets

Fixing issue #126 with Leiningen 2.5.0 due to auto-cleaning of targets being the default behaviour and thus wiping the auto-compiled main class before packing.

With this fix the auto-clean, if not set to false in project.clj, is made before compile-main.
No, it doesn't, because `leiningen.uberjar/uberjar` calls `project/merge-profiles` which goes back to the original for most of the keys of the map, which are saved into the metadata of the project hash-map:

https://github.com/technomancy/leiningen/blob/master/leiningen-core/src/leiningen/core/project.clj#L849