SMC: Compile code needs to mprotect before reading, or stale core might be run
More likely to happen in the armv8.0 runner
```
read/modify/segfault (no write made)
code cache flush
{other thread starts compiling here}
read/modify/write
{other thread finishes compiling, mprotects}
stale code gets run
```

CI failure
https://github.com/FEX-Emu/FEX/runs/6825655440?check_suite_focus=true#step:27:132
```
[DEBUG] Host CPU doesn't support atomics. Expect bad performance
[Info] Migrating to shared memory mode
Generating code on thread
Waiting for code to be modified
Modifying code from another thread
Waiting for thread to get unblocked
Thread overshoot once, this is non fatal
Thread should have been patched to not modify counter here
test failed, expected is 0 but got 1
```

Also, tear-tests should be run a statistically important number of times to catch these cases