Add regression test for tailcall VM crash

Author: morrisonlevi

ext/zend_test/tests/observer_vm_interrupt_tailcall_return.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Observer: VM interrupt during tailcall return to caller
+--DESCRIPTION--
+This exercises a VM interrupt raised immediately before a user function returns
+to a caller that invoked it through DO_FCALL. On the tailcall VM, the caller's
+saved opline must point to the opcode after DO_FCALL before a pending interrupt
+is handled.
+--EXTENSIONS--
+zend_test
+--INI--
+opcache.jit=0
+zend_test.observer.set_vm_interrupt_on_begin=1
+--FILE--
+<?php
+function interrupt_before_return(VmInterruptComparable $left, VmInterruptComparable $right): void
+{
+    $left < $right;
+}
+
+function call_interrupt_before_return(): void
+{
+    interrupt_before_return(new VmInterruptComparable(2), new VmInterruptComparable(1));
+}
+
+call_interrupt_before_return();
+echo "ok\n";
+?>
+--EXPECT--
+ok