We are marking `resholve` itself with `meta.knownVulnerabilities`, and
overriding `resholve-utils` functions's `resholve` with
`meta.knownVulnerabilities = [ ]`.
This way, we can still use `resholve` at build-time without triggering
security warnings, however we can't instantiate `resholve` itself. See:
```
$ nix-build -A resholve
error: Package ‘resholve-0.8.4’ in /.../nixpkgs/pkgs/development/misc/resholve/resholve.nix:48 is marked as insecure, refusing to evaluate.
$ nix-build -A ix
/nix/store/k8cvj1bfxkjj8zdg6kgm7r8942bbj7w7-ix-20190815
```
For debugging purposes, you can still bypass the security checks and
instantiate `resholve` by:
```
$ NIXPKGS_ALLOW_INSECURE=1 nix-build -A resholve
/nix/store/77s87hhqymc6x9wpclb04zg5jwm6fsij-resholve-0.8.4
```
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