You will need a storage-engine capable memcached and its included headers.
The easiest way to do this if you don't want to install memcached from source would be to just create a source tree and reference it.
For example, assume you keep all of your projects in ~/prog/, you
can do this:
cd ~/prog
git clone -b engine git://github.com/dustin/memcached.git
cd memcached
./config/autorun.sh
./configure
make
cd ~/prog
git clone git@github.com:northscale/ep-engine.git
cd ep-engine
./config/autorun.sh
./configure --with-memcached=$HOME/prog/memcached
make
An example invocation using the ep engine from your dev tree and
keeping the database in /tmp/ep.db looks like this:
~/prog/memcached/memcached -v -E ~/prog/ep-engine/.libs/ep.so \
-e dbname=/tmp/ep.db