compound assignment branches shall not have been TCO'd

[lhmouse]

var a = 1;
func two() { return 2;  }
func check() { return a &&= two();  }
check();
std.debug.logf("a = $1\n", a);

======================
** ASSERTION FAILED **
======================
        Condition: status == air_status_next
        Location:  asteria/src/runtime/air_node.cpp:121
        Message:
======================
terminate called without an active exception
Aborted