JDK-8282306 introduced os.is_first_C_frame_vm, but that breaks on zero since the test relies on os::current_frame(), which on all zero platforms is almost empty.

```
[ RUN ] os.is_first_C_frame_vm
/shared/projects/openjdk/jdk-jdk/source/test/hotspot/gtest/runtime/test_os.cpp:876: Failure
Value of: os::is_first_C_frame(&cur_frame)
  Actual: true
Expected: false
[ FAILED ] os.is_first_C_frame_vm (0 ms)
```

A usable fix would be to use getcontext() to implement os::current_frame() on these platforms. But let's just exclude the test for now on Zero.