mknod

1. Android provides mknod() api (unistd.h) , but not provides mknod execution file.
   
2. download the mknod.c from mknod.c
   
3. There are two way to let the mknod work
   
   1. Build with toolbox (system/core/toolbox)
      
      1. change the mknod.c main function name to mknod_main
         
      2. Modify the Android.mk
         TOOLS :=\
         .... \
         mknod
         
      3. build android, then redownload the system.img and userdata.img
         
   2. Create a new appliation
      
      1. You can crate a new application in externel folder - mknod
         
      2. Copy the mknod to new folder
         
      3. Create a Android.mk
         LOCAL_PATH:= $(call my-dir)
         include $(CLEAR_VARS)
         LOCAL_SRC_FILES:= mknod.c
         LOCAL_MODULE := mknod
         include $(BUILD_EXECUTABLE)
         
      4. build android, then redownload the system.img and userdata.img
         
4. Reference
   
   1. mknod.c