I've found by grepping for package(\_|.)*\s*\(\s*\) that many packages don't contain any package() or package_foo() functions thus they won't build. I think a few months ago makepkg was bumped to a new version and it started requiring package() from all PKGBUILDs. So, these packages will either sit at those old versions and break in close future or someone will fix them. I think the most sensible thing would be to just delete them since for such a long time no one cared to fix them. I've tried to check as hard as possible if these PKGBUILDs really don't have a package() or package_foo() but you should definetly check it the second time. Here's the list:

pcr/log4c/PKGBUILD
pcr/startupmanager/PKGBUILD
pcr/ruby-haml/PKGBUILD
pcr/python2-pkgtools/PKGBUILD
pcr/ipmiutil/PKGBUILD
pcr/python2-passlib/PKGBUILD
pcr/perl-file-find-rule/PKGBUILD
pcr/elementary-icons/PKGBUILD
pcr/newlisp/PKGBUILD
pcr/nexuiz/PKGBUILD
pcr/perl-iptables-chainmgr/PKGBUILD
pcr/bash-dynamic-completion/PKGBUILD
pcr/python2-carrot/PKGBUILD
pcr/django-extensions/PKGBUILD
pcr/perl-unix-syslog/PKGBUILD
pcr/python2-amqplib/PKGBUILD
pcr/libtorrent-extended/PKGBUILD
pcr/python-relatorio/PKGBUILD
pcr/nagios-plugins/PKGBUILD
pcr/python2-rospkg/PKGBUILD
pcr/lockfile-progs/PKGBUILD
pcr/ruby-yard/PKGBUILD
pcr/pactools/PKGBUILD
pcr/oggfwd/PKGBUILD
pcr/python2-flask-lesscss/PKGBUILD
pcr/ruby-libnotify/PKGBUILD
pcr/culmus-latex/PKGBUILD
pcr/python-paste/PKGBUILD
pcr/liblockfile/PKGBUILD
pcr/django-social-auth/PKGBUILD
pcr/emacs-js2-mode/PKGBUILD
pcr/dsh/PKGBUILD
pcr/nagios-nrpe-plugin/PKGBUILD
pcr/clx-git/PKGBUILD
pcr/xchat-otr/PKGBUILD
pcr/moblock/PKGBUILD
pcr/emacs-newlisp/PKGBUILD
pcr/nexuiz-data/PKGBUILD
pcr/python2-daemon/PKGBUILD
pcr/rakarrack/PKGBUILD
pcr/inadyn-opendns/PKGBUILD
pcr/conky-control/PKGBUILD
pcr/fpdns/PKGBUILD
pcr/jdee/PKGBUILD
pcr/python2-pydns/PKGBUILD
pcr/textext/PKGBUILD
pcr/python2-oauth2/PKGBUILD
pcr/ruby-mustache/PKGBUILD
pcr/irssi-otr-git/PKGBUILD
pcr/perl-iptables-parse/PKGBUILD
pcr/python2-eventlet/PKGBUILD
pcr/evrouter/PKGBUILD
pcr/hwd/PKGBUILD
pcr/python-paste-deploy/PKGBUILD
pcr/pyzenity/PKGBUILD
pcr/python2-argparse/PKGBUILD
pcr/ipmitool/PKGBUILD
pcr/maruku/PKGBUILD
pcr/ttf-beteckna/PKGBUILD
pcr/c-algorithms/PKGBUILD
pcr/dswm/PKGBUILD
pcr/python-xattr/PKGBUILD
pcr/psad/PKGBUILD
pcr/cgdb/PKGBUILD
pcr/ncmatrix/PKGBUILD
pcr/python-gensim/PKGBUILD
pcr/python2-fabric/PKGBUILD
pcr/emacs-bzr/PKGBUILD
pcr/elementary-gtk-theme/PKGBUILD
pcr/emacs-elib/PKGBUILD
pcr/python-wsgiref/PKGBUILD
pcr/vim-ifdef/PKGBUILD
pcr/stumpwm-git/PKGBUILD
pcr/libdshconfig/PKGBUILD
pcr/python2-empy/PKGBUILD
pcr/perl-unicode-map/PKGBUILD
pcr/postler/PKGBUILD
libre/xmlstarlet/PKGBUILD
libre/xorg-fonts-100dpi/PKGBUILD
libre/xorg-fonts-75dpi/PKGBUILD