FindwxWidgets: Look in x64 directories for MSVC (#14393)

When compiling the 64 bit version of wxWidgets using nmake the library
folders become vc_x64_lib and vc_x64_dll and can coexist with the win32
version.
Merge topic 'FindwxWidgets-msvc-x64' into next

870f91e FindwxWidgets: Look in x64 directories for MSVC (#14393)