tests: stabilize test-inherit-mode.t on FreeBSD and macOS (issue6026)

Symbolic links are funny permissions-wise, but on the linked issue
Yuya has convinced me that we can ignore this permissions issue on
macOS (FreeBSD allows setting permissions bits but ignores them) and
we'll be in fine shape.

tests/test-inherit-mode.t

@@ -70,7 +70,7 b' new directories are setgid'
   00770 ./.hg/cache/
   00660 ./.hg/cache/branch2-served
   00711 ./.hg/cache/checkisexec
-  00777 ./.hg/cache/checklink
+  007.. ./.hg/cache/checklink (re)
   00600 ./.hg/cache/checklink-target
   00660 ./.hg/cache/manifestfulltextcache (reporevlogstore !)
   00660 ./.hg/cache/rbc-names-v1