swift: drop libarclite

libarclite is needed to support ARC on very old deployment targets
(10.10 and older). None of these deployment targets are supported
deployment targets in nixpkgs, especially for Swift. This removes the
need to package the command-line tools executables.

pkgs/development/compilers/swift/compiler/default.nix

@@ -668,12 +668,6 @@ in stdenv.mkDerivation {
     # just copying the 3 symlinks inside to smaller closures.
     mkdir $lib/lib/swift/clang
     cp -P ${clang}/resource-root/* $lib/lib/swift/clang/
-
-    ${lib.optionalString stdenv.hostPlatform.isDarwin ''
-    # Install required library for ObjC interop.
-    # TODO: Is there no source code for this available?
-    cp -r ${CLTools_Executables}/usr/lib/arc $out/lib/arc
-    ''}
   '';
 
   preFixup = lib.optionalString stdenv.hostPlatform.isLinux ''