New string in translations requires clean build to work properly

[obrusvit]

It seems that adding new strings to the the firmware requires clean build after merging translations #3206.

Steps to reproduce:

1. Add new string to core/translations/en.json
2. run python core/translations/cli.py gen
3. run python core/translations/order.py
4. test a code utilizing the new string.

This results in AttributeError on my machine.

The problem might be in missing dependency of SCons and/or build.rs. Investigate and fix the issue to close this task.