Wrap use of SOCK_CLOEXEC with __linux__

This guards against the case where your clibrary defines SOCK_CLOEXEC
but the underlying network library does not support it.

lib/socket.c

@@ -93,12 +93,14 @@ static int
 create_socket(int domain, int type, int protocol)
 {
 #ifdef SOCK_CLOEXEC
-	/* Linux-specific extension (since 2.6.27): set the
+#ifdef __linux__
+    /* Linux-specific extension (since 2.6.27): set the
 	   close-on-exec flag on all sockets to avoid leaking file
 	   descriptors to child processes */
 	int fd = socket(domain, type|SOCK_CLOEXEC, protocol);
 	if (fd >= 0 || errno != EINVAL)
 		return fd;
+#endif
 #endif
 
 	return socket(domain, type, protocol);