As usual while waiting for the next release - don't forget to check the nightly builds in the forum.
Can't create object output directory /home/michael/devel/trunk/src/plugins/contrib/wxSmith/wxheaders.h.ghc
That error usually appears if you have been using (knowingly or unknowingly) a different PCH strategy before. Look into the parent directory, and delete the .gch file, then it should work fine.