(PUP-2964) Block x64 installer on Windows 2003

- Block x64 installer from running on Windows 2003 with an unsupported message
and a suggestion to use the x86 version of the MSI.
- If we find that we can move forward with backporting fixes in ruby 2, we can
remove this blocking method by reverting this change
This message should be enhanced to state "There is no Ruby on Windows build that supports x64 for Windows Server 2003. Due to this $(var.OurProductName)$(var.OurProductPlatformText) is not supported on Windows Server 2003. Please install the x86 version of the MSI.