Cleanup: Move more cmake library variables to be advanced

I noticed that there were a few variables that should not be visible per default.
It seems to me to simply be an oversight, so I went ahead and cleaned them up.

Reviewed By: Sybren, Ray molenkamp

Differential Revision: http://developer.blender.org/D14132

build_files/cmake/platform/platform_unix.cmake

@@ -362,6 +362,7 @@ if(WITH_BOOST)
       find_package(IcuLinux)
     endif()
     mark_as_advanced(Boost_DIR)  # why doesn't boost do this?
+    mark_as_advanced(Boost_INCLUDE_DIR)  # why doesn't boost do this?
   endif()
 
   set(BOOST_INCLUDE_DIR ${Boost_INCLUDE_DIRS})