mod_systemd is available since Apache 2.5. 1
You may check the version of Apache using apachectl -V
To search a linux distribution, that distributes Apache 2.5, is suggested.
1 https://httpd.apache.org/docs/trunk/mod/mod_systemd.html
##Download and compile Apache
I recommend to do this in a testing environment. I've tested it on a debian minbase wheezy system. For arch linux the package names should be almost the same and instead of apt-get, pacman should be used.
###Install build dependencies apt-get install subversion apt-get install autoconf apt-get install libtool apt-get install python apt-get install libexpat1-dev apt-get install libpcre3-dev apt-get install libsystemd-daemon-dev apt-get install g++ apt-get install make
###Download apache development source code mkdir trunk cd trunk svn co http://svn.apache.org/repos/asf/httpd/httpd/trunk ./ svn co http://svn.apache.org/repos/asf/apr/apr/trunk srclib/apr
###Configure apache ./buildconf ./configure
###Build and install make install
###Enable mod_systemd echo "LoadModule systemd_module modules/mod_systemd.so" >> /usr/local/apache2/conf/httpd.conf
###Check enabled modules /usr/local/apache2/bin/apachectl -M