dwarf expr deref fix

a.patch

commit 42bb75c3a6fe643ad15bffd3f4c273eca4fff213
Author: Yichun Zhang (agentzh) <yichun@openresty.com>
Date:   Thu Jan 21 21:29:32 2021 -0800

    bugfix: unwinder: expr: DW_OP_push*: we forgot to push the result to the dwarf stack.
    
    Most of the assembly routines in OpenSSL's libcrypto would produce unwinder failures
    and the warning "WARNING: DWARF expression stack underflow in CFI" due to this bug.

diff --git a/runtime/unwind.c b/runtime/unwind.c
index a0ef6d8b5..9cae157af 100644
--- a/runtime/unwind.c
+++ b/runtime/unwind.c
@@ -1129,6 +1129,7 @@ static int compute_expr(const u8 *expr, struct unwind_frame_info *frame,
 					goto bad_deref_size;
 				}
 			}
+		        PUSH(value);
 			break;
 
 		case DW_OP_rot: