fix: implicit declaration of function 'syscall' in apps/shell

Change-Id: Id3f56ac53ec5a3c86b04bcb7a4611f2eb77f4b80
Signed-off-by: Nuhamc <uhamc@foxmail.com>

apps/config.mk

@@ -30,7 +30,7 @@
 include $(LITEOSTOPDIR)/config.mk
 
 # common flags config
-BASE_OPTS := -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE
+BASE_OPTS := -D_FORTIFY_SOURCE=2 -D_XOPEN_SOURCE=700
 
 ASFLAGS   :=
 CFLAGS    := $(LITEOS_COPTS) $(BASE_OPTS) -fPIE

apps/shell/builtin/cd.c

@@ -29,9 +29,7 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef  _GNU_SOURCE
 #define _GNU_SOURCE
-#endif
 
 #include "unistd.h"
 #include "shcmd.h"

apps/shell/src/main.c

@@ -29,6 +29,8 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _GNU_SOURCE
+
 #include "show.h"
 #include "shmsg.h"
 #include "shcmd.h"

apps/shell/src/shmsg.c

@@ -29,6 +29,8 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _GNU_SOURCE
+
 #include "stdlib.h"
 #include "stdio.h"
 #include "unistd.h"