Fix LLDB windows build

LLDB WoA buildbot is failing due to pid_t redefinition after recent changes in
lldb/source/Plugins/ScriptInterpreter/Python/ScriptedProcessPythonInterface.cpp.
Process.h includes PosixApi.h which defines pid_t. Python.h on windows also typedefs
pid_t. To make sure that we include Python.h before PosixApi this patch renforces
the workaround previously set up to guard this issue.

https://lab.llvm.org/buildbot/#/builders/219

Reviewed By: mib

Differential Revision: https://reviews.llvm.org/D145446