Support for rpm file which does not have a dependency on /bin/sh

[tofay]

All RPMs generated by cargo-generate-rpm require /bin/sh.

This seems unnecessary, as Rust binaries don't universally require a shell. In my case I'm trying to build distroless-like containers from RPMs generated by cargo-generate-rpm, and this is causing a shell and it's dependencies to be pulled in unnecessarily.

This behaviour comes from by rpm-rs, which appears to not be maintained at present: Richterrettich/rpm-rs#54. I've raised a PR to rpm-rs/rpm#7 - which is a community fork that isn't yet publishing to crates-io.

[cat-in-136]

rpm-rs/rpm#7 has been merged to the fork of rpm-rs, which is a maintained-but-not-published-for-a-long-time community fork.

They do not care about backward compatibility. So, it is necessary to do following tasks on switching rpm-rs/rpm:

• add /bin/sh to dependency automatically, which is usually necessary
• add functionality to omit /bin/sh in dependency