Fix the versioning of Dart SDK packages

[nex3]

We used to use the /revision file in the Dart SDK to determine the version of the packages contained within, but that file has apparently disappeared. We should generate the version from the timestamp on the /create.stamp file instead.

[devoncarew]

I still see this file as existing in the latest continuous builds (http://gsdview.appspot.com/dart-editor-archive-continuous/latest/). What archive is it missing from?

[sethladd]

I made a local build, straight from source, using ./tool/build.py -m release The output dir, xcodebuild/ReleaseIA32/dart-sdk is what I point DART_SDK to.

I suspect our build process only uses "svn info", and it should use "git svn info" if "svn info" isn't working.

[munificent]

Added this to the M1 milestone.

[nex3]

I'm building from Git, and I have a revision file in my SDK output.

[sethladd]

Build script generates a revision file for both svn and git now.

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Added Fixed label.

[DartBot]

This issue has been moved to dart-lang/pub#57.