As suggested by Igor, I created a trivial PR: https://github.com/armbian/build/pull/1617
To be honest, I did not test it. I don't have enough disk space and nerves for the build machinery. So I hope I did not overlook something...
I just tripped over that too. Took me some time to figure out that /etc/environment is setting LC_ALL=C. Without any explanation and... as mentioned above, it just shouldn't do it.