I suggest:
Check your code out using svn, outside of chdkshell directory
Launch command line from chdkshell
cd <your svn working copy>
make PLATFORM=<your platform> PLATFORMSUB=<your firmware version> clean fir
chdkshell is great for people who want to just change some compile options and build the latest trunk. If you want do development and work with different versions or branches, using svn is probably a more convenient approach. chdkshell gives you a nice pre-configured toolchain.