The IL Client library is designed to make it easier to use OpenMAX on the RPi. It is not portable, but if you want to build only RPi applications (or for other Broadcom GPU systems), it can reduce the effort and frustration of using OpenMAX.
The IL Client library is not a standard library on the RPi. It is actually in the hello_pi directory, in /opt/vc/src/hello_pi/libs/ilclient/. You may have to build this yourself using the Makefile in that directory.
You can build the program in this chapter using the following Makefile: