Fix windows build after r285702, missing include to define PATH_MAX

[Ilod]

Summary

Fix the windows build after r285702.
The removal of TimeValue.h inclusion removed the inner inclusion of PosixApi.h, which defined PATH_MAX on windows, used by many other files.
Adding the PosixApi.h inclusion should not cause a problem (it only include llvm/Support/Compiler.h on non-windows platform, and the needed file on windows ones).

[labath]

I believe Zachary already fixed this.

include/lldb/Host/FileSpec.h

 // C++ Includes
 #include <functional>
 #include <string>
 
 // Other libraries and framework includes
 // Project includes
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/STLUtils.h"
+#include "lldb/Host/PosixApi.h"
 #include "lldb/lldb-private.h"
 
 namespace lldb_private {
 
 //----------------------------------------------------------------------
 /// @class FileSpec FileSpec.h "lldb/Host/FileSpec.h"
 /// @brief A file utility class.
 ///