If building from sources pulled from git, you first need to check out a copy
of gnulib:

    git clone git://git.savannah.gnu.org/gnulib.git

...once that's done, symlink gnulib-tool in that directory somewhere in your
$PATH. For instance:

    ln -s /git/gnulib/gnulib-tool ~/bin/gnulib-tool

...then run:

    ./autogen.sh

...and finally the normal:

    ./configure && make