So I have at one point had this going via Beanstalk, using Amazon Instance (2013.09) ami-35792c5c . At the time this ebextension scripts worked great when placed in the root
I was finally able to get this to work on the 2015.03 image and PostgreSQL 9.4 with a suggestion I found on the PostgreSQL yum mailing list (http://www.postgresql.org/message-id/1429688221.3808.17.camel@gunduz.org)
Specifically, I installed libpoppler straight from a CentOS 6 mirror. I also used Mike Edward's suggestion of the Amazon Linux specific pgdg rpm. In whole, it ended up being a rather simple solution, which looked like:
yum -y install http://yum.postgresql.org/9.4/redhat/rhel-6-x86_64/pgdg-ami201503-94-9.4-1.noarch.rpm
yum --enablerepo=epel -y install postgis2_94 http://centos-distro.cavecreek.net/centos/6.6/os/x86_64/Packages/poppler-0.12.4-3.el6_0.1.x86_64.rpm