Also strip the `HAREPATH` make variable embedded in the binary from
empty `$(SRCDIR)/hare/third-party`, since since nix does not follows the
FHS and relies on the `HAREPATH` environment variable to find third
party libraries.
And also:
- move platform and arch to outer let-in
- patch tzdata paths to use the nix store
- set `outputs` to `[ "out" "man" ]`
- append `nixpkgs` `hare version`'s output
- compact `postFixup` phase
- rework description
- move `binutils-unwrapped` only to `buildInputs`
[1]: https://nixpk.gs/pr-tracker.html?pr=265124
