tests: Only mock $INODE64 symbols on x86_64 macOS

tests: Only mock $INODE64 symbols on x86_64 macOS

The version of macOS running on Apple Silicon doesn't need to
concern itself with backwards compatibility with 32-bit
applications, and so it could jettison all the symbol aliasing
shenanigans involved.

https://gitlab.com/libvirt/libvirt/-/issues/121

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Tested-by: Roman Bolshakov <r.bolshakov@yadro.com>