Fix Linux build

src/Platform.c

@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include "Limelight-internal.h"
 
 // The maximum amount of time before observing an interrupt

src/Platform.h

@@ -25,7 +25,6 @@
 #include <netinet/in.h>
 #include <psp2/kernel/threadmgr.h>
 #else
-#define _GNU_SOURCE
 #include <unistd.h>
 #include <pthread.h>
 #include <sys/time.h>