Ok, thanks.lib32 just wasn't implemented. The linux support is brand new but I forgot about lib32. DragonFly doesn't have these. I imagine it's not difficult to implement (e.g. one additional if on freebsd)
I ran into a potential issue with java/openjdk8 myself (socket timeout trying to connect to VM) so I'd be interested to hear if anyone has trouble with that one. I suspect the builders minimal /etc/services is missing a port/protocol there.
FWIW, I just finished building java/openjdk8 on CURRENT with synth(1) and had no obvious issues on my machine, at least not that I noticed thus far. It's still got 400+ ports to go however.