Fix: Do not embed (dirty) in the docker built version

[junderw]

I noticed all the docker builds have (dirty) string in their versions.

It's because Dockerfile's COPY . . doesn't copy Dockerfile because it's ignored by docker by default.

So git sees this as "you deleted Dockerfile but haven't committed it" and the status is dirty.

[knorrium]

utACK

[junderw]

FYI: I found the problem by pushing a tag on my personal repo and adding git status --short before the cargo build step in Dockerfile.

It showed Dockerfile was deleted on the git status.

Then I verified this fixed it by adding some logging to the build file and trying to build locally after deleting Dockerfile manually.

Self tACK