gcc.dg/attr-copy-6.c: Require visibility.

[Hans-Peter Nilsson]

Another trivial one, committed.

gcc/testsuite:
	* gcc.dg/attr-copy-6.c: Require visibility.

--- gcc/gcc/testsuite/gcc.dg/attr-copy-6.c.orig	Mon Jan 13 22:30:47 2020
+++ gcc/gcc/testsuite/gcc.dg/attr-copy-6.c	Sun Jul 19 05:44:12 2020
@@ -2,6 +2,7 @@
    { dg-do compile }
    { dg-skip-if "Attributes not supported" { { hppa*-*-hpux* } && { ! lp64 } } }
    { dg-options "-O2 -Wall" }
+   { dg-require-visibility "hidden" }
    { dg-require-alias "" }
    { dg-require-weak "" } */