Make the pub build step depend on the async/await compiled sources.

Make the pub build step depend on the async/await compiled sources.

R=nweiz@google.com

Committed: https://code.google.com/p/dart/source/detail?r=40125

[Bob Nystrom, 2014-09-10 20:19:13]

rnystrom@google.com changed reviewers:
+ nweiz@google.com, ricow@google.com

[Bob Nystrom, 2014-09-10 20:19:14]

This should make it so that running build.py will always pick up changes in the
generated code.

It doesn't pick up changes to the async/await source, but that's deliberate: it
also doesn't invoke the async/await compiler so watching those sources won't be
helpful.

The idea is that compiling the stuff in pub/ over to pub_generated/ is outside
of the purview of the build system entirely.

[nweiz, 2014-09-10 21:05:22]

lgtm

[Bob Nystrom, 2014-09-10 22:39:54]

Committed patchset #1 (id:1) manually as 40125 (presubmit successful).