alsa doesn't seem mandatory for phonon-kde (I've successfuly built it on BSD, obviously without alsa), please make it optional. This is a requirement for having kde-4 on BSD.
I was running into the same problem under an ordinary Linux. And I think I got it working the same way like you. I just removed the alsa dependency from the ebuild. And amarok-2 is working flawless without any alsa library. Thus, same ask from me. Please make the alsa-lib optional, depending on the alsa USE-Flag. Thanx in advance.
I bumped into this, too. I got fed up with ALSA on my laptop, and was moving it to OSS4, when this turned up. I removed the alsa-lib dependency from a test ebuild; the configuration phase DOES check up the existence of ALSA, but compiles & works happily without it.
Done, Thanks for report.