When attempting to build the Minidump Diagnostics project from the UE4 source, it will fail if you're using Visual Studio 2015 Update 2. Please note that this does not occur in the base VS2015 or with Update 1.
The error messages are different for 4.11.2 and 4.12. Logs attached.
Head over to the existingAnswerHub thread and let us know what's up.