darwin: 10.11 → 10.12

Lots of stuff has gotten moved around. Many security libraries have been merged
into the Security monorepo. I’ve cleared them out for now, we will
need to modify Security to build them!

This also moves some things around to more clearly separate
bootstrapping the stdenv from everything else. We want the “normal”
mode to be the non-bootstrapped version. When you ask for “Security”,
you want the actual built software, not a crippled one.

- Add TARGET_OS_OSX to darwin.libSystem. Looks like something
  introduced in 10.12. TARGET_OS_MAC is only set when building for
  desktop (iOS will have TARGET_OS_MAC set)
- Bump darwin.dtrace
- Bump darwin.libpthread
- Remove SmartCardServices, libsecurity*, etc.
- Install some more headers for darling.