FYI:
There were some changes to FindLibical.cmake the past couple days.

If you want to build your kcalcore against self-installed libical3 using kdesrc-build, do this:

In your kdesrc-buildrc, inside the 'global' section add the line
  set-env PKG_CONFIG_PATH /usr/local/lib64/pkgconfig

adapt the path to where you installed libical3

I did find a nasty threading bug in libical3 that hits OSX so there will be a 3.0.2 release "coming soon"