Not in 7.1

Unknown command-line switch: /xp64

...

/Debug   - Create a Debug configuration build environment
/Release - Create a Release configuration build environment
/x86     - Create 32-bit x86 applications
/x64     - Create 64-bit x64 applications
/ia64    - Create 64-bit ia64 applications
/vista   - Windows Vista applications
/xp      - Create Windows XP SP2 applications
/2003    - Create Windows Server 2003 applications
/2008    - Create Windows Server 2008 or Vista SP1 applications
/win7    - Create Windows 7 applications
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