Support incremental builds

[tadatuta]

Now each time any block is changed we are to rebuild the whole bundle which takes some time for huge projects.

[narqo]

I suspect support for streaming build results without writing a lot of stuff on the disk (e.g. directly from memory) will be more useful for dev-servers.

[tadatuta]

@narqo That's true, @cody- has already switched to tmpFS on build farm and got boost.

[j0tunn]

I'm @j0tunn now :)

[voischev]

👍