[gssdp] build: Update pktinfo test for Apple as well

[Jens Georg <jensgeorg src gnome org>]

commit 7cda968752810751b7f0f6dc0bfbab7a844176d7
Author: Jens Georg <mail jensge org>
Date:   Thu Nov 29 12:01:35 2018 +0100

    build: Update pktinfo test for Apple as well

 meson.build | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/meson.build b/meson.build
index d7e5560..8d6a90d 100644
--- a/meson.build
+++ b/meson.build
@@ -9,6 +9,9 @@ conf.set_quoted('VERSION', meson.project_version())
 
 # Check for struct in_pktinfo
 pktinfo_test = '''#define _GNU_SOURCE
+#ifdef __APPLE__
+#define __APPLE_USE_RFC_3542
+#endif
 #include <netinet/ip.h>
 struct in_pktinfo pktinfo;
 struct in6_pktinfo pktinfo6;