libc++, libc++abi, lldb: fix 3.8

[Ralith]

Motivation for this change

When LLVM and clang were updated to 3.8, libc++, libc++abi, and lldb were skipped, leaving them with incorrect hashes and broken builds. This gets them building again.

I don't have OSX to test on, so the tweaked darwin patch should be reviewed by someone who does.

This fix should probably be backported to all branches that contain llvm 3.8, including nixos-16.03.

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • OS X
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[mention-bot]

By analyzing the blame information on this pull request, we identified @andrewrk and @acowley to be potential reviewers

[vcunat]

The bad hashes were fixed a about month ago #15252. Your merge base is older than that (nixpkgs channel is very old now). But the rest of the fixes was still missing.