[skip ci] Document LDFLAGS not being unset anymore

Author: Girgias

UPGRADING.INTERNALS

@@ -72,6 +72,9 @@ PHP 8.3 INTERNALS UPGRADE NOTES
 2. Build system changes
 ========================
 
+* LDFLAGS are not unset anymore allowing them to be adjusted e.g.
+  LDFLAGS="..." ./configure
+
 * Removed the HAVE_DEV_URANDOM compile time check.  HAVE_DEV_URANDOM will
   now never be defined. Any checks relying on HAVE_DEV_URANDOM should be
   removed.  Even with HAVE_DEV_URANDOM it was not guaranteed that