Clean old build artifacts

[thedodd]

Currently, Trunk will continue to accumulate artifacts in the dist dir as changes continue to take place. This can be a bit overwhelming, and is something we should clean-up.

One approach may be to build a manifest of paths generated per build. At the very end of the build, we will go through the dist dir and remove anything which was not generated as part of the current build.

proposed design

• introduce a new sub dir of dist, let's call it .current, which represents the artifacts being accumulated in the current build.
• dist/.current will be deleted before any new build is started.
• as the very final step of a successful build, we will delete the contents of the dist dir (except for the .current dir), and then immediately move all of the contents of dist/.current up into dist.

This will ensure that we do not continuously accumulate artifacts as builds take place, and will also ensure that artifacts are not prematurely deleted in case of application compilation errors on the user's behalf.

[ranile]

For some context on where it can lead to:

That ended up happening in a short amount of time

[thedodd]

Closed by #108