Cleanup: Fix build error with MSVC

`BLI_cpu_support_sse41` needs BLI_System.h.

Reviewers: brecht

source/blender/blenlib/BLI_system.h

@@ -19,6 +19,10 @@
 
 #include <stdio.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** \file
  * \ingroup bli
  */
@@ -53,4 +57,8 @@ int BLI_system_memory_max_in_megabytes_int(void);
 #  define BLI_SYSTEM_PID_H <unistd.h>
 #endif
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* __BLI_SYSTEM_H__ */

source/blender/compositor/operations/COM_DenoiseOperation.cpp

@@ -21,6 +21,7 @@
 
 #include "COM_DenoiseOperation.h"
 #include "BLI_math.h"
+#include "BLI_system.h"
 #ifdef WITH_OPENIMAGEDENOISE
 #  include "BLI_threads.h"
 #  include <OpenImageDenoise/oidn.hpp>

source/blender/editors/space_node/drawnode.c

@@ -24,6 +24,7 @@
 
 #include "BLI_blenlib.h"
 #include "BLI_math.h"
+#include "BLI_system.h"
 
 #include "DNA_node_types.h"
 #include "DNA_object_types.h"