testsuite - Require alias support for pr90760.

This test fails on Darwin because it requires alias support, so
add the relevant dg-requires.

2019-06-13  Iain Sandoe  <iain@sandoe.co.uk>

	* gcc.dg/pr90760.c: Require alias support.

From-SVN: r272248

gcc/testsuite/ChangeLog

+2019-06-13  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* gcc.dg/pr90760.c: Require alias support.
+
 2019-06-13  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR tree-optimization/90869

gcc/testsuite/gcc.dg/pr90760.c

 /* PR c/90760 */
 /* { dg-do compile } */
+/* { dg-require-alias "" } */
 /* { dg-require-named-sections "" } */
 
 void bar (void) {}