I'm trying to build kdevelop from source, so I'm working through building all the kde packages.

I got through qt okay, but emerge kdelibs fails on phonon-vlc. It gets to 100% on the build, and then when it tries linking everything, I get hundreds of "undefined reference to _imp___ZN6Phonon*" messages.

Google hasn't turned up anything helpful. Any ideas what might be wrong?

this is a problem with phonon HEAD and phonon-vlc 0.4.1 so just try to build phonon 4.5.1 .
emerge --target=4.5.1 phonon and then try to rebuild phonon-vlc.

If you're living in a timezone compatible to europe you can also ask such questions in irc://irc.freenode.net/kde-windows else it could get hard to reach someone awake