linux-x86-zero build failure

32 bit zero build gets this failure:

rc/hotspot/os/linux/os_linux.cpp:5321:3: error: 'workaround_expand_exec_shield_cs_limit' was not declared in this scope
[2020-06-24T01:08:37,486Z] 5321 | workaround_expand_exec_shield_cs_limit();
[2020-06-24T01:08:37,487Z] | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The way that os.hpp includes platforms, requires duplicating os_linux_x86.hpp declarations in os_linux_zero.hpp:

From os.hpp:
  // Platform dependent stuff
#ifndef _WINDOWS
# include "os_posix.hpp"
#endif
#include OS_CPU_HEADER(os) <==== os_linux_zero.hpp
#include OS_HEADER(os) <==== os_linux.hpp

The 32 bit build also fails because of JDK-8214854 but that's a different issue.