tools: moveconfig: check directory location before compilers

tools: moveconfig: check directory location before compilers

We must ensure this tool is run from the top of source directory
before calling update_cross_compile().  Otherwise, the following
exception is thrown:

Traceback (most recent call last):
  File "./moveconfig.py", line 918, in <module>
    main()
  File "./moveconfig.py", line 908, in main
    update_cross_compile()
  File "./moveconfig.py", line 292, in update_cross_compile
    for arch in os.listdir('arch'):
OSError: [Errno 2] No such file or directory: 'arch'

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>