anchor.diff:  
   let
     log_level = "info";
  -in stdenv.mkDerivation {
  +
  +# XXX: using 'gcc9Stdenv' to get lld linking. Replace with 'stdenv' once NixOS
  +# has gcc9 as the default version.
  +in gcc9Stdenv.mkDerivation {
     name = "rust-env";
     buildInputs = [
       rustup
  
positive.code:   '';
  
    # Set Environment Variables
    RUST_BACKTRACE = 1;
  
    RUST_LOG = "calx-ecs=${log_level},vitral=${log_level},calx=${log_level},display=${log_level},world=${log_level},magog=${log_level}";
  
  }
  
negative.code:     xorg.libXcursor
      xorg.libXi
      xorg.libXrandr
  
      # Linker
      lld
  
      # SPIR-V shader compiler
      shaderc
  