code: def get_default_arch(env):
      
      arch = env.get('MSVS_ARCH', 'x86')
  
      msvs = InstalledVSMap.get(env['MSVS_VERSION'])
  
      if not msvs:
          arch = 'x86'
      elif not arch in msvs.get_supported_arch():
          fmt = "Visual Studio version %s does not support architecture %s"
          raise SCons.Errors.UserError(fmt % (env['MSVS_VERSION'], arch))
  
      return arch
docs: Return the default arch to use for MSVS
  
      if no version was requested by the user through the MSVS_ARCH environment
      variable, select x86
  
      Return
      ------
      arch: str