Testsuite: mark IPA test as requiring alias support

This was indicated in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85656
but never committed. Without it, the test fails on darwin.

gcc/testsuite/ChangeLog:
	* gcc.dg/ipa/ipa-icf-38.c: Require alias support.

gcc/testsuite/gcc.dg/ipa/ipa-icf-38.c

@@ -1,4 +1,5 @@
 /* { dg-do link } */
+/* { dg-require-alias "" } */
 /* { dg-options "-O2 -fdump-ipa-icf-optimized -flto -fdump-tree-optimized" } */
 /* { dg-require-effective-target lto } */
 /* { dg-additional-sources "ipa-icf-38a.c" }*/