check-meta: fix 'hasNoMaintainers' (#412184)

pkgs/stdenv/generic/check-meta.nix

···
   hasUnfreeLicense = attrs: hasLicense attrs && isUnfree attrs.meta.license;
 
   hasNoMaintainers =
+    # To get usable output, we want to avoid flagging "internal" derivations.
+    # Because we do not have a way to reliably decide between internal or
+    # external derivation, some heuristics are required to decide.
+    #
+    # If `outputHash` is defined, the derivation is a FOD, such as the output of a fetcher.
+    # If `description` is not defined, the derivation is probably not a package.
+    # Simply checking whether `meta` is defined is insufficient,
+    # as some fetchers and trivial builders do define meta.
     attrs:
-    (attrs ? meta.maintainers && (length attrs.meta.maintainers) == 0)
-    && (attrs ? meta.teams && (length attrs.meta.teams) == 0);
+    (!attrs ? outputHash)
+    && (attrs ? meta.description)
+    && (attrs.meta.maintainers or [ ] == [ ])
+    && (attrs.meta.teams or [ ] == [ ]);
 
   isMarkedBroken = attrs: attrs.meta.broken or false;