Download from https://github.com/systemd/systemd/archive/v234.tar.gz
(change version as appropriate).

$ patch -Np1 -i ../systemd-234-make-dist.patch
$ ./autogen.sh
$ ./configure --prefix=/usr
$ make -C docs
$ make -C man
$ make dist

The distribution tarball will be placed directly in the source tree as
systemd-234.tar.xz.