final: prev: let
  lib = final.lib;
  fixLLVM = pkg: let
    stdenv = pkg.stdenv or final.stdenv;
    isCross = stdenv.hostPlatform != stdenv.buildPlatform;
  in pkg.overrideAttrs (old: if !isCross then {} else {
    cmakeFlags = let
      flags = old.cmakeFlags or [];
      filtered = builtins.filter (f: !(lib.hasPrefix "-DLLVM_TABLEGEN=" f)) flags;
      tblgen = "${final.buildPackages.llvmPackages_9.llvm}/bin/llvm-tblgen";
    in filtered ++ [ "-DLLVM_TABLEGEN=${tblgen}" ];
  });
in {
  llvmPackages_9 = prev.llvmPackages_9 // {
    llvm = fixLLVM prev.llvmPackages_9.llvm;
  };
  llvm_9 = final.llvmPackages_9.llvm;
}