I have attempted to load my library using the Build System (PublicAdditionalLibraries and PublicLibraryPaths) but the library is not loading that way. I removed the PublicAdditionLibraries entry and attempted to load my library with a pragma call which also failed. Once that was done I made sure that the path was correct by using the fully qualified (and escaped) path in the pragma call and it worked fine.
I ended up putting together the following hack to get the build working properly:
basically I am just defining a constant and passing it in at built time.
I am now able to link via the build system, the catch being that the PublicLibrariesPath list is not allowing me to put in the path on my other drives and the libs are being searched for in the install directory for UE4. I have confirmed this by passing the full path through to the PublicAdditionalLibraries list and confirmed that my libraries are being found. I will push a fix for this when i get to the root cause in the build system.
Until then, the following will allow anyone who is waiting for a fix: