Minor Dockerfile Improvements

[aminvakil]

https://docs.docker.com/develop/develop-images/dockerfile_best-practices/ :

In addition, cleaning up the apt cache and removing /var/lib/apt/lists helps keep the image size down.
Since the RUN statement starts with apt-get update, the package cache will always be refreshed prior to apt-get install.

https://github.com/hadolint/hadolint/wiki/SC2046 : Quote the find output which has another command's output that may contain white spaces to cause word splitting.

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[aminvakil]

@googlebot I signed it!

[aminvakil]

This results in a 18MB reduction on final image from 535MB to 517MB :)

[tooryx]

Hi @aminvakil,

Thank you for your contribution. I will take a look at it soon, but could I kindly ask that you sync against the master branch as the initial PR is a bit old (apologies for this)?

Thank you, ~tooryx

[aminvakil]

Hi @aminvakil,

Thank you for your contribution. I will take a look at it soon, but could I kindly ask that you sync against the master branch as the initial PR is a bit old (apologies for this)?

Thank you, ~tooryx

Hi @tooryx

No problem at all, after all this is not a "must have" improvement. I've done the rebasing, please tell me if there is any other changes necessary for this PR to get merged.

[tooryx]

Thank you @aminvakil! I will review it in the following days.

~tooryx