busybox filesystem add ldd function

/********************************************************************
 *               busybox filesystem add ldd function
 * 声明：
 *     本文主要是为了解决缪新建提出的查看程序涉及到动态链接库的问题。
 *
 *                                 2016-1-23 深圳 南山平山村 曾剑锋
 *******************************************************************/

一、参考文章：
    where is 'ldd'?
        http://buildroot-busybox.2317881.n4.nabble.com/where-is-ldd-td48070.html

二、解决办法：
    1. You really don't need a special ldd. ldd is just a script. In its most basic usage (ldd <executable>), it just runs: 
        # LD_TRACE_LOADED_OBJECTS=1 <executable> 
    2. For example on busybox: 
        # LD_TRACE_LOADED_OBJECTS=1 /bin/busybox 
            linux-vdso32.so.1 =>  (0x00100000) 
            libc.so.6 => /lib/libc.so.6 (0x0fe70000) 
            /lib/ld.so.1 (0x48000000 

三、测试效果：
    [zengjf@root ]# LD_TRACE_LOADED_OBJECTS=1 /bin/busybox
            libm.so.6 => /lib/libm.so.6 (0x2ac8c000)
            libc.so.6 => /lib/libc.so.6 (0x2acf6000)
            /lib/ld-linux-armhf.so.3 (0x2aae1000)
    [zengjf@root ]# LD_TRACE_LOADED_OBJECTS=1 /bin/main
    hello world.
    [zengjf@root ]# ls
    main    mainso
    [zengjf@root ]# LD_TRACE_LOADED_OBJECTS=1 /bin/mainso
            libc.so.6 => /lib/libc.so.6 (0x2abea000)
            /lib/ld-linux-armhf.so.3 (0x2ab1b000)
    [zengjf@root ]#