One of our build servers has just been updated to the latest \"Microsoft SQL Server Update for database tooling\" (version 12.0.60629.0) and is now incompatible with the ver
This is an issue introduced in a recent SSDT update. It has been fixed internally and is targeted for inclusion in the next (16.4) release of SSDT. SSDT releases are initially released via the SSDT download page with notifications on the SSDT Team Blog, and then roll out over Visual Studio Extensions and Updates within 2-3 weeks (as this goes on a separate VS-wide schedule).
Disclosure: I work on the SSDT team
Install the latest DacFx on the build server or change from using the sqlpackage.exe in the msi to the nuget version of the DacFx usnig:
https://blogs.msdn.microsoft.com/ssdt/2016/08/22/releasing-ssdt-with-visual-studio-15-preview-4-and-introducing-ssdt-msbuild-nuget-package/
If this makes dacpac's not backwards compatible then I would raise a connect item for it and see if it a bug, if not it would be good if there was notification of this sort of thing and a connect item should get that rolling.
Ed