Where is `configure' script in the emacs source tree?

[Navy Cheng]

Hi,
I want to compile and install emacs from the source. So I clone 
`https://github.com/emacs-mirror/emacs.git' to my laptop.

1. git clone https://github.com/emacs-mirror/emacs.git
2. cd ./emacs
3. git checkout emacs-24.5
4. git branch -b mybr

I think I get the emacs-24.5 source now. The I read README and INSTALL. In 
INSTALL:

> 2a. `cd' to the directory where you unpacked Emacs and invoke the
>      `configure' script:
>
>                ./configure

But I can't find configure in the repository. Where is `configure'?