Fix line endings of entrypoint script on Windows

[bwRavencl]

Use dos2unix to ensure that the line endings of the entrypoint script are automatically corrected.

Please check out https://willi.am/blog/2016/08/11/docker-for-windows-dealing-with-windows-line-endings/ for more details regarding this issue.

[wborn]

It might be better to add a .gitattributes file to the repo instead with text eol=lf for such files so the files are always cloned with the correct line endings.

See: https://help.github.com/en/github/using-git/configuring-git-to-handle-line-endings