Cleanup: quiet CMake warnings from use of undefined variables

intern/ghost/CMakeLists.txt

@@ -138,12 +138,17 @@ if(WITH_INPUT_NDOF)
     intern/GHOST_NDOFManager.hh
   )
 
+  # Only some platforms define this.
+  if(DEFINED NDOF_INCLUDE_DIRS)
     list(APPEND INC_SYS
       ${NDOF_INCLUDE_DIRS}
     )
+  endif()
+  if(DEFINED NDOF_LIBRARIES)
     list(APPEND LIB
       ${NDOF_LIBRARIES}
     )
+  endif()
 endif()
 
 list(APPEND SRC

source/blender/blenloader_core/CMakeLists.txt

@@ -6,6 +6,8 @@ set(INC
   PUBLIC .
 )
 
+set(INC_SYS
+)
 
 set(SRC
   intern/blo_core_bhead.cc