Where is the configure script?

[jpoprof]

In the file README there is the following section:

If you have downloaded a Nettle release, build it with the usual
./configure && make && make check && make install (see the INSTALL
file for further instructions).

But there is no file named "configure" in the git archive.
I understand that probably the file "configure.ac" is meant to be used with autoconf tools. But that should be mentioned in the documentation.

When I run first autoconf and then ./configure then I get the following error:

config.status: creating libhogweed.map
config.status: error: cannot find input file: `config.h.in'

There really is no config.h.in in the git project. Is it supposed to be generated by autoconf somehow?
By the way, I am curently running this in cygwin on windows.
I try to build release 3.5.1..

Thanks for any help.