There is support for just about any build system. For some, there is a more or less complete implementation, but not part of the main repo. But first, clone the main repo.

$ git clone git://git.savannah.gnu.org/gnucap.git/
$ cd gnucap
$ git checkout develop # as of 17.02.20

$ git clone git://git.savannah.gnu.org/gnucap/gnucap-tools.git --branch autotools autotools
$ ./autotools/bootstrap
$ mkdir build
$ cd build
$ ../configure.gnu --help
$ less ../autotools/README

and

$ ../configure.gnu
[..]
$ make
$ main/gnucap
[..]
gnucap>

$ git clone git://git.savannah.gnu.org/gnucap/gnucap-tools.git --branch cmake cmake
$ mkdir build
$ cd build
$ less ../cmake/README

and

$ cmake ../cmake
[..]
$ make
$ main/gnucap
[..]
gnucap>