One could register a callable object(normally a function) via RegisterPreBuildingAction in SConscript. It will be called when PreBuilding get invoked. PreBuilding should be called before the building procedure. It is currently used by RTGUI to generate the minimal perfect hash code when all the source files are scanned(i.e. just before building).

Maybe we should invoke PreBuilding in DoBuilding.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2353 bbd45198-f89e-11dd-88c7-29a3b14d5316