[CFI] Disable cfi-icall checking for test helper

It's not possible to use GeneratedCode for this test because the called
stubs use the stdcall calling convention but GeneratedCode does not allow
specifying a custom calling convention.

BUG=v8:7164

Change-Id: Ic28c4313bb2b68103b94e4c1ae7c037a789edce2
Reviewed-on: https://chromium-review.googlesource.com/1008994Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52558}

test/cctest/test-code-stubs.cc

@@ -94,7 +94,7 @@ void RunOneTruncationTestWithTest(ConvertDToICallWrapper callWrapper,
   CHECK_EQ(to, result);
 }
 
-
+DISABLE_CFI_ICALL
 int32_t DefaultCallWrapper(ConvertDToIFunc func,
                            double from) {
   return (*func)(from);