rfkill was subsumed by util-linux in 2017 [1], and the upstream has not
been updated in over 5 years [2]. This package shadows the rfkill from
util-linux, so it can be completely removed with no breaking changes,
because util-linux is in the base package set in nixos/system-path.
[1] d17fb726b5
[2] https://git.sipsolutions.net/rfkill.git/log/
Whenever we create scripts that are installed to $out, we must use runtimeShell
in order to get the shell that can be executed on the machine we create the
package for. This is relevant for cross-compiling. The only use case for
stdenv.shell are scripts that are executed as part of the build system.
Usages in checkPhase are borderline however to decrease the likelyhood
of people copying the wrong examples, I decided to use runtimeShell as well.
