Properly Cache Options

[ryanmrichard]

CMakePP assumes that options that are being passed to dependencies need to be cached. This is usually the case when a user sets the command on the command line or in a toolchain file; however, if users are setting the options in the CMakeLists.txt they do not get cached. CMakePP needs to avoid cacheing options set like this.

This was brought up in
NWChemEx/PluginPlay#119