How to execute code in the normal OS when I am inside a `buildFHSUserEnv`?

[hmenke]

This gets asked like once a week. Quoting my answer from another thread:

`sudo` does not work from within vscode-fhs

It is impossible to use SUID applications from within user namespaces for good reason. Otherwise an unprivileged user could simply bind a crafted /etc/sudoers and become root.