Don't track internal class dependencies

Subtyping relationships established on internal classes are always
going to hold (if we ignore Windows), so there is no need to
explicitly track them.

This fixes an assertion failure in GH-7251.

Author: nikic

Zend/zend_inheritance.c

@@ -376,13 +376,17 @@ static void track_class_dependency(zend_class_entry *ce, zend_string *class_name
 		return;
 	}
 
+#ifndef ZEND_WIN32
+	/* On non-Windows systems, internal classes are always the same,
+	 * so there is no need to explicitly track them. */
+	if (ce->type == ZEND_INTERNAL_CLASS) {
+		return;
+	}
+#endif
+
 	ht = (HashTable*)CG(current_linking_class)->inheritance_cache;
 
-#ifndef ZEND_WIN32
-	if (ce->type == ZEND_USER_CLASS && !(ce->ce_flags & ZEND_ACC_IMMUTABLE)) {
-#else
 	if (!(ce->ce_flags & ZEND_ACC_IMMUTABLE)) {
-#endif
 		// TODO: dependency on not-immutable class ???
 		if (ht) {
 			zend_hash_destroy(ht);