drivers: nsos: fcntl: prefer Zephyr-specific macros over libc

Definitions of fcntl flags are different between native libc and Zephyr. In
order to correctly map those values to the host, include Zephyr's fcntl.h
header, instead of the one bundled with libc.

Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>

drivers/net/nsos_fcntl.c

@@ -16,7 +16,14 @@
  * symbols.
  */
 
+/*
+ * When building for Zephyr, use Zephyr specific fcntl definitions.
+ */
+#ifdef __ZEPHYR__
+#include <zephyr/posix/fcntl.h>
+#else
 #include <fcntl.h>
+#endif
 
 #include "nsos_errno.h"
 #include "nsos_fcntl.h"