rand/rand_unix.c: address macro redifinition warning.

Occasionally, e.g. when compiling for elderly glibc, you end up passing
-D_GNU_SOURCE on command line, and doing so triggered warning...

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6616)

diff --git a/crypto/rand/rand_unix.c b/crypto/rand/rand_unix.c
index b64cf278255007128af660d79448e9f861738f02..f482de063a9438c1e6f03be1889aa9d1a859d80f 100644 (file)
--- a/crypto/rand/rand_unix.c
+++ b/crypto/rand/rand_unix.c
@@ -7,7 +7,9 @@
  * https://www.openssl.org/source/license.html
  */
 
-#define _GNU_SOURCE
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
 #include "e_os.h"
 #include <stdio.h>
 #include "internal/cryptlib.h"