git doesn't support "-C" args under 1.8.5 occurs in configure.ac

as I noticed from git release notes in 1.8.5: 

 * Just like "make -C <directory>", "git -C <directory> ..." tells Git
   to go there before doing anything else.

So we should have some conditional statements in configure.ac around git checkpoint, otherwise we got error message which is :

Unknown option: -C
usage: git [--version] [--help] [-c name=value]
           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
           [-p|--paginate|--no-pager] [--no-replace-objects] [--bare]
           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
           <command> [<args>]