duperemove: encode absolute path to lscpu

Without the change `duperemove` fails to run in parallel
if `PATH` is missing `lscpu` as:

    $ PATH= ./result/bin/duperemove /tmp
    sh: line 1: lscpu: No such file or directory
    Gathering file list...
    No dedupe candidates found.

Noticed when wrote a minimal systemd timer for `duperemove`.

pkgs/tools/filesystems/duperemove/default.nix

@@ -1,5 +1,6 @@
 { lib, stdenv, fetchFromGitHub, libgcrypt
-, pkg-config, glib, linuxHeaders ? stdenv.cc.libc.linuxHeaders, sqlite }:
+, pkg-config, glib, linuxHeaders ? stdenv.cc.libc.linuxHeaders, sqlite
+, util-linux }:
 
 stdenv.mkDerivation rec {
   pname = "duperemove";
@@ -12,6 +13,11 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-WjUM52IqMDvBzeGHo7p4JcvMO5iPWPVOr8GJ3RSsnUs=";
   };
 
+  postPatch = ''
+    substituteInPlace util.c --replace \
+      "lscpu" "${lib.getBin util-linux}/bin/lscpu"
+  '';
+
   nativeBuildInputs = [ pkg-config ];
   buildInputs = [ libgcrypt glib linuxHeaders sqlite ];