Require a 64-bit host binary to spawn a 64-bit guest.

For HVF this is trivially true because macOS 11 dropped
support for 32-bit applications entirely.

For NVMM, NetBSD only enables nvmm on x86_64:
  http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/dev/nvmm/Makefile?rev=1.1.6.2;content-type=text%2Fplain

For WHPX, we have already dropped support for 32-bit Windows.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 meson.build | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/meson.build b/meson.build
index 911955cfa8..85317cd63f 100644
--- a/meson.build
+++ b/meson.build
@@ -319,13 +319,11 @@ else
 endif
 accelerator_targets += { 'CONFIG_XEN': xen_targets }
 
-if cpu in ['aarch64']
+if cpu == 'aarch64'
   accelerator_targets += {
     'CONFIG_HVF': ['aarch64-softmmu']
   }
-endif
-
-if cpu in ['x86', 'x86_64']
+elif cpu == 'x86_64'
   accelerator_targets += {
     'CONFIG_HVF': ['x86_64-softmmu'],
     'CONFIG_NVMM': ['i386-softmmu', 'x86_64-softmmu'],
-- 
2.43.0