Calvin, Baho,
I rebuilt the libcaldav PKGBUILD I did to use Tim's quickbuild source as suggested by Serghei. The updated PKGBUILD is here:
http://www.3111skyline.com/dl/dt/trinity/arch/src/trinity-libcaldav.tar.gz
Let me know if you find anything wrong with it. Hopefully it will fix the kdepim build error with -DWITH_CALDAV=ON