Create the full path instead of just the leaf directory. On a fresh sync of...

Create the full path instead of just the leaf directory. On a fresh sync of the depot, the build directories don't exist and the function fails.

BUG=
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/14121017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@194021 0039d316-1c4b-4281-b951-d872f2087c98