Fix ifunc detection in target-supports.exp file.

2018-03-08  Thomas Schwinge  <thomas@codesourcery.com>

	* lib/target-supports.exp: Do not return zero from a ifunc
	function.

From-SVN: r258362

gcc/testsuite/ChangeLog

+2018-03-08  Thomas Schwinge  <thomas@codesourcery.com>
+
+	* lib/target-supports.exp: Do not return zero from a ifunc
+	function.
+
 2018-03-08  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/84746

gcc/testsuite/lib/target-supports.exp

@@ -448,8 +448,9 @@ proc check_ifunc_available { } {
 	#ifdef __cplusplus
 	extern "C" {
 	#endif
-	typedef void F (void);
-	F* g (void) { return 0; }
+	extern void f_ ();
+ 	typedef void F (void);
+	F* g (void) { return &f_; }	
 	void f () __attribute__ ((ifunc ("g")));
 	#ifdef __cplusplus
 	}