[net][at] Add AT Socket select LIBC configure.

components/net/at/Kconfig

@@ -61,6 +61,7 @@ if RT_USING_AT
             
         config AT_USING_SOCKET
             bool "Provide similar BSD Socket API by AT"
+            select RT_USING_LIBC
             default n
     endif
 

components/net/at/at_socket/at_socket.c

@@ -26,6 +26,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <sys/time.h>
 
 #include <at_socket.h>
 

components/net/sal_socket/SConscript

@@ -23,8 +23,8 @@ if GetDepend('SAL_USING_POSIX'):
     if not GetDepend('HAVE_SYS_SELECT_H'):
         CPPPATH += [cwd + '/include/dfs_net/sys_select']
 
-    if not GetDepend('HAVE_SYS_SOCKET_H'):
-        CPPPATH += [cwd + '/include/socket/sys_socket']
+if not GetDepend('HAVE_SYS_SOCKET_H'):
+    CPPPATH += [cwd + '/include/socket/sys_socket']
 
 group = DefineGroup('SAL', src, depend = ['RT_USING_SAL'], CPPPATH = CPPPATH)