Support insecure builds for docker?

[vn971]

Currently, RUA does not support building packages without the namespace jail (bubblewrap). Unfortunately, it does not work in e.g. docker.

Adding support for insecure (jail-less) builds could help users of docker, see e.g. https://github.com/vn971/rua/issues/6#issuecomment-442188061

[vn971]

If anybody thinks it's very important and wants to write a PR for that, I think it could be merged presuming:

• it's a quality PR in terms of code and maintenance
• the feature itself is hidden under a verbose-only warning flag

Personally, I see too few evidence on needing that.

[gwpl]

bwrap: capset failed: Operation not permitted
2022-10-13 09:37:29 [ERROR] - Failed to run bwrap.
2022-10-13 09:37:29 [ERROR] - A possible cause is if RUA itself is run in jail (docker, bwrap, firejail,..).
2022-10-13 09:37:29 [ERROR] - If so, see https://github.com/vn971/rua/issues/8

[gwpl]

cross-linking: I've started thread on Arch Linux forum referring to this issue: https://bbs.archlinux.org/viewtopic.php?pid=2063741#p2063741