yaml-cpp include directory ends up in the wrong place

[nsoblath]

How I found the problem: I built and installed Cicada, and the directory structure in include looks like this:

include
    |
    Cicada
    |   |
    |   Scarab
    |   |
    |   rapidjson
    |
    yaml-cpp

yaml-cpp should be inside Cicada just like rapidjson.

[nsoblath]

I check on 7/2/18 and I wasn't able to determine why the dependencies get installed differently.

The one possibility I found was that rapidjson defined INCLUDE_INSTALL_DIR as a cache variable, whereas yaml-cpp did not. When I tried switching that variable to a cache variable in PackageBuilder.cmake, it didn't change anything.