Move editor/build/truncate_files.py to tools/create_timestamp_file.py
Move editor/build/truncate_files.py to tools/create_timestamp_file.py

We need this in more gyp files, so moving it to a common location

R=ahe@google.com

Review URL: https://codereview.chromium.org//247103002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@35250 260f80e4-7a28-3924-810f-c04153c831b5

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