If pcsx2 is compiled for 32-bits and then compiled for 64-bits without
cleaning the build files, the wrong wx3.0 manifest will be included. The
same will happen vice versa.
Place the generated rcdefs.h file in a platform specific directory so
the correct manifest will always be used.
This lets wxWidgets3.0 build even when the full pathname has non ASCII
characters or spaces in it.
Note that pcsx2 and some of the plugins that rely on custom build
commands still fail.