Except in special wrapper environments like `python3.withPackages`,
where all "build" dependencies are also runtime dependencies,
`propagatedBuildInputs` doesn't actually encode runtime dependencies.
It's meant to propagate build dependencies to dependants, so the
dependants don't have to explicitly add them to their `buildInputs`.
With `wrapProgram`, you can now run rr without having gdb
installed (eg. `nix run nixpkgs#rr replay`).
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