- [x] Have you followed the [guidelines for contributing](https://github.com/snapcore/snapcraft/blob/master/CONTRIBUTING.md)? - [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? - [x] If this is a bugfix. Have you checked that there is a bug report open for the issue you are trying to fix on [bug reports](https://bugs.launchpad.net/snapcraft)? - [x] If this is a new feature. Have you discussed the design on the [forum](https://forum.snapcraft.io)? - [x] Have you successfully run `./runtests.sh static`? - [x] Have you successfully run `./runtests.sh unit`? ----- Currently, Snapcraft organizes during the stage step. This is terrible for two reasons: 1. The organization actually occurs in the installdir, which belongs to the build step. As a result, a snap that uses the `organize` keyword cannot in some cases be staged twice (i.e. have the stage step cleaned, and then staged again) because the organization cannot always happen twice. 2. Since organization only happens in the stage step, and collision detection runs before any parts are staged, collision detection doesn't take the organization into account. As a result, one cannot use the `organize` keyword to get around file collisions between parts, even though we recommend it for exactly that use. This PR fixes #2031 and LP: [#1628098](https://bugs.launchpad.net/snapcraft/+bug/1628098) by completing the organization at the tail end of the build step, so the part is already organized when it comes time to check for collisions and stage.