patchutils: enable and fix strictDeps (#485444)

pkgs/tools/text/patchutils/generic.nix

@@ -26,6 +26,10 @@ stdenv.mkDerivation rec {
   # tests fail when building in parallel
   enableParallelBuilding = false;
 
+  preConfigure = ''
+    export PERL=${perl.interpreter}
+  '';
+
   postInstall = ''
     for bin in $out/bin/{splitdiff,rediff,editdiff,dehtmldiff}; do
       wrapProgram "$bin" \
@@ -44,6 +48,8 @@ stdenv.mkDerivation rec {
       -exec sed -i '{}' -e 's|/bin/echo|echo|g' \;
   '';
 
+  strictDeps = true;
+
   meta = {
     description = "Tools to manipulate patch files";
     homepage = "http://cyberelk.net/tim/software/patchutils";