Add support for FreeRTOS and lwIP (#166)

Add support for FreeRTOS and lwIP

Signed-off-by: Jeroen Koekkoek <jeroen@koekkoek.nl>

src/ddsrt/cmake/ifaddrs.c

@@ -0,0 +1,23 @@
+/*
+ * Copyright(c) 2006 to 2018 ADLINK Technology Limited and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Eclipse Distribution License
+ * v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+ */
+#include "dds/ddsrt/ifaddrs.h"
+
+#if DDSRT_WITH_LWIP
+# if LWIP_SOCKET
+#   error "cmake_HAVE_IFADDRS=lwip"
+# else
+#   error "cmake_HAVE_IFADDRS=false"
+# endif
+#else
+# error "cmake_HAVE_IFADDRS=true"
+#endif
+