Fix machine code on macOS 11
macOS 11 adds two JIT hardening features:
* Memory can only be mmapped as both PROT_WRITE and PROT_EXEC if MAP_JIT
is also specified.
* Memory mapped with MAP_JIT is never writeable and executable at the same
time. It is necessary to call a function before writing, and then again
after writing to make it executable again.
Merge remote-tracking branch 'origin/master' into new_utf8
Merge remote-tracking branch 'origin/8.1' into gobject-introspection
ARM64: Enable disassembler even without PIKE_DEBUG
ARM64: preliminary check_threads_etc
Uses dedicated register for the fast_check_threads_etc counter but
is generated in too many places for now.
ARM64: complete fast check threads
Slow path now only generated once per program.
ARM64: do some checks only during init
ARM64: added disassembler
ARM64: implement OPCODE_INLINE_BRANCH
ARM64: implement QUICK and comparison jumps
ARM64: Initial commit