Build hygiene: Ensure that no packages compute their hash based on files that we .gitignore

[mads-hartmann]

Some Leeway packages include files that we have in .gitignore in their source declarations, which means that the hash of the package is different in a Gitpod Workspace (due to builds performed as part of our prebuilds I believe) than in our Werft builds.

A temporary solution has been implemented in #14156 but we should fix the package definitions properly.

To see what packages needs out attention: Start a new workspace, modify dev/preview/workflow/preview/build.sh by removing git clean -dfX and adding --dry-run to the leeway invocation.

[mads-hartmann]

This is breaking some workflows for developers, so worth prioritising now that people are using leeway run dev:preview ☺️ More context here

[mads-hartmann]

A suggestion from Chris:

this is a great place to introduce a leeway vet rule for that checks if node_modules is part of the resolved sources.
We have source related rules for docker already.

I think this would be great way to tackle the problem.

1. Extend vet to detect the kinds of files that are causing problems (node_modules, dist folders, etc)
2. Bump Leeway in the workspace. Run leeyway vet and fix all the problems
3. Remove the deletion of the files in build.sh

[gtsiolis]

Cross-posting a temporary workaround for visibility until this gets properly resolved, see relevant discussion (internal).

... for those wanting to use telepresence after running leeway run dev:preview, do yarn && yarn build first in /workspace/gitpod [1].

Cc @laushinka @mads-hartmann @svenefftinge @csweichel

[mads-hartmann]

I created gitpod-io/leeway#140 to extend leeway to make it easier to find files in srcs that are .gitignored but I don't think I'll need it to solve this specific issue as I already made a lot of progress https://github.com/gitpod-io/gitpod/pull/15120/files