stdenv/check-meta: Don't create new environments when computing meta.repository

pkgs/stdenv/generic/check-meta.nix

@@ -10,7 +10,9 @@ let
     concatMapStrings
     concatMapStringsSep
     concatStrings
+    filter
     findFirst
+    head
     isDerivation
     length
     concatMap
@@ -436,6 +438,18 @@ let
     # -----
     else { valid = "yes"; });
 
+  getRepository = let
+    getSrcs = attrs:
+      if attrs ? src
+      then
+        [ attrs.src ]
+      else
+        filter (src: src ? meta.homepage) attrs.srcs;
+    getHomePages = map (src: src.meta.homepage);
+    unlist = list:
+      if length list == 1 then head list
+      else list;
+    in attrs: unlist (getHomePages (getSrcs attrs));
 
   # The meta attribute is passed in the resulting attribute set,
   # but it's not part of the actual derivation, i.e., it's not
@@ -454,22 +468,7 @@ let
       # this could be handled a lot easier if we nulled it instead
       # of having it be undefined, but that wouldn't match the
       # other attributes.
-      repository = let
-        getSrcs = attrs:
-          if attrs ? src
-          then
-            [ attrs.src ]
-          else
-            lib.filter (src: src ? meta.homepage) attrs.srcs;
-        getHomePages = srcs: map (src: src.meta.homepage) srcs;
-        unlist = list:
-          if lib.length list == 1
-          then
-            lib.elemAt list 0
-          else
-            list;
-      in
-        unlist (getHomePages (getSrcs attrs));
+      repository = getRepository attrs;
     } // {
       # `name` derivation attribute includes cross-compilation cruft,
       # is under assert, and is sanitized.