Just to clarify the details that Adel's linked eclipse forum covers, here's how I solved this (on OS X):
Note: for me, even though my personal environment (i.e. if in bash, echo $PATH) had /Developer/usr/bin in it, I still had to add it to Eclipse's Environment variables:
Go to Eclipse Preferences -> C/C++ -> Build -> Environment -> Add.. -> "${PATH}:/Developer/usr/bin"
In the case of some other OS, just use the right path where make exists.