Revert "pkgs/top-level/stage.nix: add pkgsLLVMLibc"

This reverts commit 41b14024d24bd7488b58d7a252f8f16b194d57f9.

lib/systems/default.nix

···
               "uclibc"
             else if final.isAndroid then
               "bionic"
-            else if final.isLLVMLibc then
-              "llvm"
             else if
               final.isLinux # default
             then
···
           # don't support dynamic linking, but don't get the `staticMarker`.
           # `pkgsStatic` sets `isStatic=true`, so `pkgsStatic.hostPlatform` always
           # has the `staticMarker`.
-          isStatic = final.isWasi || final.isRedox || final.isLLVMLibc;
+          isStatic = final.isWasi || final.isRedox;
 
           # Just a guess, based on `system`
           inherit

lib/systems/inspect.nix

···
         uclibceabi
         uclibceabihf
       ];
-    isLLVMLibc = [ { abi = abis.llvm; } ];
 
     isEfi = [
       {

lib/systems/parse.nix

···
     };
     uclibc = { };
 
-    # LLVM libc
-    llvm = { };
-
     unknown = { };
   };
 

pkgs/top-level/release-attrpaths-superset.nix

···
 
     # cross packagesets
     pkgsLLVM = true;
-    pkgsLLVMLibc = true;
     pkgsMusl = true;
     pkgsStatic = true;
     pkgsCross = true;

pkgs/top-level/release.nix

···
           "x86_64-linux"
           "aarch64-linux"
         ];
-        pkgsLLVMLibc.stdenv = [
-          "x86_64-linux"
-          "aarch64-linux"
-        ];
         pkgsArocc.stdenv = [
           "x86_64-linux"
           "aarch64-linux"

pkgs/top-level/stage.nix

···
       }
     );
 
-  makeLLVMParsedPlatform =
-    parsed:
-    (
-      parsed
-      // {
-        abi = lib.systems.parse.abis.llvm;
-      }
-    );
-
   stdenvAdapters =
     self: super:
     let
···
       crossSystem = stdenv.hostPlatform // {
         useLLVM = true;
         linker = "lld";
-      };
-    };
-
-    pkgsLLVMLibc = nixpkgsFun {
-      overlays = [
-        (self': super': {
-          pkgsLLVMLibc = super';
-        })
-      ] ++ overlays;
-      # Bootstrap a cross stdenv using LLVM libc.
-      # This is currently not possible when compiling natively,
-      # so we don't need to check hostPlatform != buildPlatform.
-      crossSystem = stdenv.hostPlatform // {
-        config = lib.systems.parse.tripleFromSystem (makeLLVMParsedPlatform stdenv.hostPlatform.parsed);
-        libc = "llvm";
       };
     };