Fix code warning.

Change-Id: Ib11fb49f528d3688351ae349d5b4e307c28b3967
diff --git a/mbtk/mbtk_adbd/src/main.c b/mbtk/mbtk_adbd/src/main.c
index 036ba24..f52f1d4 100755
--- a/mbtk/mbtk_adbd/src/main.c
+++ b/mbtk/mbtk_adbd/src/main.c
@@ -8,6 +8,7 @@
 #include <time.h>
 #include <sys/time.h>
 #include <termios.h>    //UART
+#include <pthread.h>
 
 #include "mbtk_log.h"
 #include "mbtk_adb_info.h"
@@ -194,7 +195,10 @@
 
             LOGD("CONN_SUCCESS");
 
-            chdir("/");
+
+            if(chdir("/")) {
+                LOGE("chdir / fail.");
+            }
             break;
         }
         case MBTK_ADB_MSG_PUSH:
@@ -267,7 +271,7 @@
                 LOGD("Kill cmd:%s", shell_cmd + 6);
                 char cmd[1024] = {0};
                 snprintf(cmd,1024,"kill `pidof %s | awk '{print $1}'`", shell_cmd + 6);
-                system(cmd);
+                mbtk_system(cmd);
             } else {
                 LOGE("Kill Command/AT error.");
             }