New solution for tests in static libraries ! (MSVC)

[Lectem]

I encountered some issues today because of the static linking defaults of MSVC which removes unreferenced symbols, and found a solution that doesn't involve build system tricks !

You can actually fix this by using the /OPT:NOREF linker flag.
Obvisouly it is not always what you want as it might make bigger .lib files, but I think it is fine if you only add it for Tests enabled builds.