WHPX: Fix WHPX build break

With upstream commit#8a19980e, logic was introduced to only
allow WHPX build on x64. But, the logic checks for the cpu family
and not the cpu. On my fedora container build, the cpu family is
x86 and the cpu is x86_64. Fixing the build break by checking for
the cpu, instead of the cpu family.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Message-Id: <SN4PR2101MB0880D706A85793DDFC411304C01D0@SN4PR2101MB0880.namprd21.prod.outlook.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -204,7 +204,7 @@ else
   have_xen_pci_passthrough = false
 endif
 if not get_option('whpx').disabled() and targetos == 'windows'
-  if get_option('whpx').enabled() and cpu != 'x86_64'
+  if get_option('whpx').enabled() and host_machine.cpu() != 'x86_64'
     error('WHPX requires 64-bit host')
   elif cc.has_header('WinHvPlatform.h', required: get_option('whpx')) and \
        cc.has_header('WinHvEmulation.h', required: get_option('whpx'))