unused parameter warnings should not cause errors on non-release builds

**Is your feature request related to a problem? Please describe.**
Treating all warnings as errors may not be the best approach for productivity. Sometimes I turn on/off certain parts of the code, which often triggers `unused parameter` warnings (treated as errors), which are tedious to resolve.

**Describe the solution you'd like**
Consider mofifying https://github.com/eic/epic/blob/d14e80b98cc51fb7acf014f6984caf8fe347aed1/CMakeLists.txt#L26-L29

Should we be less strict for non-release builds?