include-what-you-use: fix llvm references

pkgs/development/tools/analysis/include-what-you-use/default.nix

···
-{ lib, stdenv, fetchurl, cmake, llvmPackages, python2 }:
+{ lib, stdenv, fetchurl, cmake, llvmPackages, python3 }:
 
 stdenv.mkDerivation rec {
   pname = "include-what-you-use";
···
     url = "${meta.homepage}/downloads/${pname}-${version}.src.tar.gz";
   };
 
-  buildInputs = with llvmPackages; [ clang-unwrapped llvm python2 ];
-  nativeBuildInputs = [ cmake ];
+  nativeBuildInputs = with llvmPackages; [ cmake llvm.dev llvm clang-unwrapped python3];
+  buildInputs = [ llvmPackages.libclang ];
 
   cmakeFlags = [ "-DIWYU_LLVM_ROOT_PATH=${llvmPackages.clang-unwrapped}" ];