busybox

build system: specify '-nostldlib' when linking to .o files

For certain cross build scenarios the LD variable is overridden
to use the gcc executive to ensure all the target tuning parameters
are used.  In these cases, the executive errors out as shown below
but since this step is only linking to a .o file the standard libs
are not needed.

    $ make LD=gcc applets/built-in.o
      LD      applets/built-in.o
    /usr/bin/ld: cannot find -lgcc_s
    /usr/bin/ld: cannot find -lgcc_s
    collect2: ld returned 1 exit status
    make[1]: *** [applets/built-in.o] Error 1
    make: *** [applets_dir] Error 2

Signed-off-by: Drew Moseley <drew_moseley@mentor.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>