linkIntoOwnPackage: make pathsToLink introspectable/injectable by consumers

pkgs/by-name/trivial-builders/package.nix

@@ -48,13 +48,20 @@
   in
     runCommandLocalOverridable "${pkg.pname or pkg.name}-${suffix}" ({
       outputs = [ "out" ] ++ lib.optionals wantMan' [ "man" ];
+      pathsToLink = paths;
+      configurePhase = ''
+        runHook preConfigure
+        # all vars supplied by nix are str, so convert -> array
+        concatTo pathsToLink pathsToLink
+        runHook postConfigure
+      '';
     } // args) ''
       tryLink() {
         local srcPath="$1/$2"
         local dirName=$(dirname "$2")
         test -e "$srcPath" && mkdir -p "$out/$dirName" && ln -s "$srcPath" "$out/$2"
       }
-      for item in ${lib.escapeShellArgs paths}; do
+      for item in "''${pathsToLink[@]}"; do
         tryLink "${bin}" "$item" ||
           tryLink "${man}" "$item" ||
           tryLink "${out}" "$item" ||