edencommon: add update script

(cherry picked from commit c7b019d5f7)
(cherry picked from commit c60de83718e9f89f91c2ede5922e77d466233229)

pkgs/by-name/ed/edencommon/package.nix

@@ -17,6 +17,8 @@
   gtest,
   apple-sdk_11,
   darwinMinVersionHook,
+
+  nix-update-script,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -95,6 +97,8 @@ stdenv.mkDerivation (finalAttrs: {
     )
   '';
 
+  passthru.updateScript = nix-update-script { };
+
   meta = {
     description = "Shared library for Meta's source control filesystem tools (EdenFS and Watchman)";
     homepage = "https://github.com/facebookexperimental/edencommon";