tests: "cp -a" is a GNUism

diff --git a/RelNotes b/RelNotes
index 53d76d1a47e0750b0d8b14287ff3d923ca55b438..9cd9140a6b6e8ee15dc2b237795b1117b0140842 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.12.1.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.12.3.txt
\ No newline at end of file