Fix Zephyr build

Author: embhorn

src/wolfio.c

@@ -25,8 +25,11 @@
 #endif
 
 /* Enable GNU extensions for accept4() on Linux/glibc. Must be defined
- * before any system headers are included. */
-#if !defined(_WIN32) && !defined(_GNU_SOURCE)
+ * before any system headers are included. Excluded for Zephyr and other
+ * embedded RTOSes whose libc layers conflict with glibc-style definitions
+ * (e.g., Zephyr's socket_select.h vs. glibc's fd_set). */
+#if (defined(__linux__) || defined(__ANDROID__)) && \
+    !defined(__ZEPHYR__) && !defined(_GNU_SOURCE)
     #define _GNU_SOURCE 1
 #endif
 
@@ -1630,8 +1633,8 @@ int wolfIO_TcpBind(SOCKET_T* sockfd, word16 port)
 int wolfIO_TcpAccept(SOCKET_T sockfd, SOCKADDR* peer_addr, XSOCKLENT* peer_len)
 {
     int fd;
-#if !defined(USE_WINDOWS_API) && defined(SOCK_CLOEXEC) && \
-    (defined(__linux__) || defined(__ANDROID__))
+#if !defined(USE_WINDOWS_API) && !defined(__ZEPHYR__) && \
+    defined(SOCK_CLOEXEC) && (defined(__linux__) || defined(__ANDROID__))
     fd = (int)accept4(sockfd, peer_addr, peer_len, SOCK_CLOEXEC);
 #else
     fd = (int)accept(sockfd, peer_addr, peer_len);