Ensure "clean" target matches --destination flag

[colinrotherham]

I noticed when we build to a custom directory via --destination it's not "cleaned"

npx gulp build:package --destination 'custom/location/package'
npx gulp build:dist --destination 'custom/location/dist'

☝️ As those two commands only clean ./package via cleanPackage() and ./dist via cleanDist()

This PR includes:

1. Automatic destination based on task name build:package or build:dist
2. Automatic clean target based on destination
3. Tests for --destination if we want to keep it
4. Removal of --destination if we want to get rid of it

This comment was really useful: #2243 (comment)

[owenatgov]

One tiny question. This looks great to me!

It's probs worth getting a js squad dev to look over this still as I'm rusty on these build scripts and conventions that we're trying to follow with these tooling updates.

[domoscargin]

Part of me wants to do this by parsing the task name, but this is way less fussy and prone to errors!

[domoscargin]

I think this looks grand!

Maybe at this stage it makes sense to keep the --destination flag until we've completed work to scope our JavaScript/Browser support changes, in case we make some big changes that require liberal use of it.

I think that's unlikely to happen, but it probably makes sense to keep our options open, and we can always come back and get rid of it down the line.

[colinrotherham]

Thanks @domoscargin

Did you see the "remove" commit was 1 of 3?

I'm more than happy to drop that one, keeping the automatic clean() target + new test coverage?

[domoscargin]

@colinrotherham

Yup, sorry, should've been clearer - I think we should do exactly that. Was just holding off approving to see if you were on the same page.

I'll approve now and we can drop that commit.

[domoscargin]

🏆