Fix GH-16851: JIT_G(enabled) not set correctly on other threads

There doesn't seem to be a thread post-startup hook that runs after
zend_startup_cb() that could be used for this

this fix is similar to accel_startup_ok() as seen here: https://github.com/php/php-src/blob/fc1db70f106525e81f9a24539340b7cf2e82e844/ext/opcache/ZendAccelerator.c#L2631-L2634

Closes GH-16853.

NEWS

@@ -27,6 +27,8 @@ PHP                                                                        NEWS
 - Opcache:
   . Fixed bug GH-16770 (Tracing JIT type mismatch when returning UNDEF).
     (nielsdos, Dmitry)
+  . Fixed bug GH-16851 (JIT_G(enabled) not set correctly on other threads).
+    (dktapps)
 
 - OpenSSL:
   . Prevent unexpected array entry conversion when reading key. (nielsdos)

ext/opcache/ZendAccelerator.c

@@ -3283,6 +3283,8 @@ static zend_result accel_post_startup(void)
 				if (JIT_G(buffer_size) != 0) {
 					zend_accel_error(ACCEL_LOG_WARNING, "Could not enable JIT!");
 				}
+			} else {
+				zend_jit_startup_ok = true;
 			}
 		}
 #endif

ext/opcache/jit/zend_jit.c

@@ -103,6 +103,8 @@ typedef struct _zend_jit_stub {
 #define JIT_STUB(name, offset, adjustment) \
 	{JIT_STUB_PREFIX #name, zend_jit_ ## name ## _stub, offset, adjustment}
 
+bool zend_jit_startup_ok = false;
+
 zend_ulong zend_jit_profile_counter = 0;
 int zend_jit_profile_counter_rid = -1;
 
@@ -5096,6 +5098,13 @@ static void zend_jit_reset_counters(void)
 
 ZEND_EXT_API void zend_jit_activate(void)
 {
+#ifdef ZTS
+	if (!zend_jit_startup_ok) {
+		JIT_G(enabled) = 0;
+		JIT_G(on) = 0;
+		return;
+	}
+#endif
 	zend_jit_profile_counter = 0;
 	if (JIT_G(on)) {
 		if (JIT_G(trigger) == ZEND_JIT_ON_HOT_COUNTERS) {

ext/opcache/jit/zend_jit.h

@@ -91,6 +91,8 @@ typedef struct _zend_jit_trace_rec zend_jit_trace_rec;
 typedef struct _zend_jit_trace_stack_frame zend_jit_trace_stack_frame;
 typedef struct _sym_node zend_sym_node;
 
+extern bool zend_jit_startup_ok;
+
 typedef struct _zend_jit_globals {
 	bool enabled;
 	bool on;