[Export] Use auto-increment build number in export versions.

[bruvzg]

Adds application/config/build project setting which is automatically incremented on successful export and used as (unless overridden in the export settings) iOS/macOS machine-readable version (CFBundleVersion), Android versionCode and 4-th component of app/file version on Windows.

See #83686 (comment)

[fire]

How would I set this in cicd?

[akien-mga]

I'm not sure it's a good idea to auto-increment this number. The build number is an important piece of metadata for some platforms and here it would increase any time an export is done, including when exporting for different platforms one at a time. So the Windows, macOS, Linux, etc. builds would have a different number for what is technically still the exact same version of the project.

I think the build number is something users should still consciously increment - or at least there should be an option to choose if it should be auto-incremented on export or not.

In case it's not auto-incremented, we need to think about the UX so that it's still easy for users to change it when they do have project changes that they want reflected in a change of the build number.

Inferring it from VCS is also something that could be worth considering as an option, where e.g. for Git the build number could be the number of commits in the repo. This doesn't account for unstaged changes which would still affect the build though.