revert for all platforms except win32 to the old ROOTBUILD behaviour. For
Win32 introduce a new winrtdebug flag that is turned on during
./configure --build=debug OR when ROOTBUILD contains "debug" during
./configure.


git-svn-id: http://root.cern.ch/svn/root/trunk@14229 27541ba8-7e3a-0410-8455-c3a389f83636