How to add version tag to my product?

You probably need to use a shell script before build to specify the value of Version and Version_time, and modify from here:

    /* For example:
    Version=v1.0
    Version_time=14:35
    */

    /* To link id.o for all the :: targets */
    .INSERT.%.COMMAND: .ID.o

    .ID.o : .MAKE .VIRTUAL .REPEAT .FORCE .IGNORE
	    $(<<) : id.o

    /* To create id.c as ANSI C or C++ code, and you have to declare
       char* stampid;
       somewhere in your source code
     */ 
    id.c : (Version) (Version_time) .SPECIAL
	    cat >$(<) <<'!'
	    void sTaMpSUB(){
		    extern char *stampid;
		    stampid="@(#)MY_PROD(Alcatel-Lucent) $(Version) $(Version_time)";
	    }
	    !

If the above rules are put in the global makefile, the rules will apply to all the '::' targets in the product. You may want to put the rules only in those leaf makefiles which build the targets that you want the 'what' string to appear.

For a similar example, see the Sablime page How To Version Tag Your Product.