Bump build number without using `CURRENT_PROJECT_VERSION`
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Since [I can't bump my build number](http://stackoverflow.com/questions/11737325/agvtool-new-version-and-what-version-do-not-correspond) using agvtool I am wondering if there is a quick way to bump the build number in my project using the command line.

I would rather not have to parse the plist's XML if this is possible.