removes redundant builds when watching

[EverlastingBugstopper]

turns out wranglerjs already implements #1219 (correct me if im wrong @xtuc - we call compiler.watch when we pass --watch=1 to wranglerjs)

the problem was that we would start a wranglerjs process with --watch=1 at the beginning, but then we'd also run a regular blocking wrangler js build after code was changed. this should speed up live reload by at least 2x...? probably? haven't actually benchmarked but this change should make a noticeable difference.

cc @PierBover this is relevant to your interests 😄

[xtuc]

Sorry I can't remember. DIdn't you implemented https://github.com/cloudflare/wrangler/blob/master/wranglerjs/index.js#L158-L159?

[EverlastingBugstopper]

nah - must have been @xortive. not sure where to even find the docs on using webpack as a library

[PierBover]

Thanks for the mention!