Fixes docgen build step on Windows. Also addresses dartbug.com/4989 by using docgen from freshly created sdk.
Fixes docgen build step on Windows.
Also addresses dartbug.com/4989 by using docgen from freshly created sdk.

BUG=dartbug.com/4989
BUG=dartbug.com/18392
R=alanknight@google.com, ricow@google.com

Review URL: https://codereview.chromium.org//246563005

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@35348 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk