Defer to host for networking/DNS

[facekapow]

Darling currently does DNS resolution itself. Ideally, we should instead defer to the host's libc for networking calls. That way, we get the host's networking/DNS setup "for free".

Problem

• Darling's current networking setup is disjoint from the host's setup.
  • We have our own resolv.conf which has its own DNS servers, different from what the user might want on the host.
  • This means that, if users want the same setup in Darling, they'll need to duplicate their work and make sure to keep it in sync with their host configuration.
• There are certain additional configurations which can be set up on the host that would require significant work to support in Darling with the current model (e.g. mDNS resolution).

Solution

• Use libelfloader to call into the host's libc and have it perform DNS resolution for us.
  • It should be okay to keep using Apple's libinfo, because it's modular and actually uses resolvers to perform the resolution.
  • What would have to change is our current darling-resolver; it would need to make libelfloader calls instead of calling into libresolv.
  • Similarly, we should modify libresolv to call into the host (for applications that use it directly). This one will require a bit more intrusion (i.e. function replacement).