[LIB:ARBITER] Addendum to 374f2b4d: Fix build.

- No need to use a PCH when compiling a 1-file library.
- Add the _NTSYSTEM_ definition.

- Since the arbiter.h file is to be included by the users of this
  library, namely only kernel-mode NT components (incl. NTOS), there
  is no need to include the standard kernel-mode headers in it.
  Include these headers instead in the private implementation of the
  library, arbiter.c.

sdk/lib/drivers/arbiter/CMakeLists.txt

@@ -1,10 +1,8 @@
 
-include_directories(${REACTOS_SOURCE_DIR}/sdk/lib/rtl)
+add_definitions(-D_NTSYSTEM_)
 
 list(APPEND SOURCE
-    arbiter.c
-    arbiter.h)
+    arbiter.c)
 
 add_library(arbiter ${SOURCE})
 add_dependencies(arbiter bugcodes xdk)
-add_pch(arbiter arbiter.h SOURCE)

sdk/lib/drivers/arbiter/arbiter.c

@@ -8,11 +8,14 @@
 
 /* INCLUDES *******************************************************************/
 
-#define NDEBUG
-#include <debug.h>
+#include <ntifs.h>
+#include <ndk/rtltypes.h>
 
 #include "arbiter.h"
 
+#define NDEBUG
+#include <debug.h>
+
 /* GLOBALS ********************************************************************/
 
 /* DATA **********************************************************************/

sdk/lib/drivers/arbiter/arbiter.h

@@ -9,11 +9,6 @@
 #ifndef _ARBITER_H
 #define _ARBITER_H
 
-#ifndef _NTOSKRNL_
-#include <ntifs.h>
-#include <ndk/rtlfuncs.h>
-#endif
-
 typedef struct _ARBITER_ORDERING
 {
     ULONGLONG Start;