Describe the bug

checkInputs are added to nativeBuildInputs but not buildInputs when doCheck is set, so libs added to checkInputs cannot be found by compilers when strictDeps is true.

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/make-derivation.nix#L150-L151

Steps To Reproduce

with import <nixpkgs> {};
stdenv.mkDerivation {
  name = "whatever";
  checkInputs = [ zlib ];
  nativeBuildInputs = [ pkg-config ];
  doCheck = true;
  strictDeps = true;
  buildCommand = ''
    pkg-config --cflags zlib
    touch $out
  '';
}

When strictDeps is set, pkg-config fails to find zlib, whereas it finds it without strictDeps.

Note: needing libs in checkInputs is very common in ocamlPackages.