configurable shortcuts are already on the long list of feature requests. But here's a hack, if you're willing to edit zipped XML files:
Under codeblocks directory, there's the share/codeblocks subdirectory. There are two files: compiler_gcc.zip and debugger_gdb.zip.
WARNING! It is
VERY IMPORTANT that you backup these files first! Otherwise you can make codeblocks crash.
You'll see compiler_menu.xrc and debugger_menu.xrc.
Edit them with an xml editor (codeblocks can edit xml files, btw), and change the shortcuts.
After you're done, zip the files into their corresponding zips, and restart codeblocks.
If everything goes well, you'll be able to use your old shortcuts!