mach_vm_remap() allows to create a dual mapping without having to
use a file descriptor, which has to open a file or shm memory. The
problem is that the recent macos version started displaying a popup
message when such file is opened and that annoyed a lot of users.
Thus, the initial code-path is no longer used, and mach_vm_remap()
is used instead.
This change only applies for x86 macs. Apple silicon doesn't allow
dual mapping and instead uses MAP_JIT.
