pkgs: add substituteSubset

pkgs/default.nix

@@ -14,4 +14,6 @@ final: prev: {
   sim65 = final.callPackage ./sim65.nix { };
 
   unbted = final.callPackage ./unbted.nix { };
+
+  substituteSubset = final.callPackage ./substitute-subset.nix { };
 }

pkgs/substitute-subset.nix

@@ -0,0 +1,27 @@
+{ lib, stdenv }:
+
+args:
+
+stdenv.mkDerivation ({
+  name = if args ? name then args.name else baseNameOf (toString args.src);
+  builder = builtins.toFile "builder.sh" ''
+    source $stdenv/setup
+    set -o pipefail
+
+    eval "$preInstall"
+
+    args=
+
+    cp -r "$src" "$out"
+
+    pushd "$out"
+    echo -ne "${lib.concatStringsSep "\\0" args.files}" | xargs -0 -n1 -I {} -- find {} -type f -print0 | while read -d "" line; do
+      substituteAllInPlace "$line"
+    done
+    popd
+
+    eval "$postInstall"
+  '';
+  preferLocalBuild = true;
+  allowSubstitutes = false;
+} // args)