Update Ant build to support multiple build configurations.
Update Ant build to support multiple build configurations.

Enables building both upstream in chromium and in the downstream fork.

Review URL: https://chromiumcodereview.appspot.com/9837099

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@129633 0039d316-1c4b-4281-b951-d872f2087c98

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