Fix race condition in zend_runtime_jit(), zend_jit_hot_func()

[arnaud-lb]

Fixes GH-19889.

zend_runtime_jit() prevents concurrent compilation with zend_shared_alloc_lock(), but this doesn't prevent blocked threads from trying to compile the function again after they acquire the lock.

In the case of GH-19889, one of the function entries is compiled with zend_jit_handler(), which fails when the op handler has been replaced by a JIT'ed handler.

This can be produced with this script:

function f(int $a, int ...$b) {
    // RECV $a
    // RECV_VARIADIC $b: second entry, compiled with zend_jit_handler()
    // RETURN $b
    return $b;
}

$f = 'f';
var_dump($f(1,2));

Fix by marking compiled functions with a new flag ZEND_FUNC_JITED, and skipping compilation of marked functions. The same fix is applied to zend_jit_hot_func().

[dktapps]

A/B test confirmed this fixes my application's issue 👍🏻