Use correct feature test macro for qsort_r detection

diff --git a/configure b/configure
index 96bacd218639c43d218a4c879ba4f839235bf14f..9f2b342cd940fbc1a70f6ee9a754796752f2db65 100755 (executable)
--- a/configure
+++ b/configure
@@ -270,7 +270,7 @@ int test ( void )
 }' -lpthread
 
 check_cc_snippet qsort_r '
-#define __USE_GNU
+#define _GNU_SOURCE
 #include <stdlib.h>
 #define TEST test
 int test(void)