S390: Support circular references between generated builtins.

Port 266be35b

    Minor fix to the original CL.

R=yangguo@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I10a4d64aa010118b669374e604fe8ed0104ec77f
Reviewed-on: https://chromium-review.googlesource.com/598808Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#47095}

src/s390/code-stubs-s390.cc

@@ -1122,7 +1122,10 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
     __ Call(BUILTIN_CODE(isolate(), JSEntryTrampoline), RelocInfo::CODE_TARGET);
   }
 
+  // Unlink this frame from the handler chain.
+  __ PopStackHandler();
   __ bind(&exit);  // r2 holds result
+
   // Check if the current stack frame is marked as the outermost JS frame.
   Label non_outermost_js_2;
   __ pop(r7);