multiarch libraries for cross-compiling from Ubuntu 14.04

I'm trying to develop for BBB by cross-compiling from Ubuntu. My app uses libao and libmpg123, and as far as I can tell, there aren't armhf versions available in apt. What's the recommended approach here? Just download the sources and build for armhf, then link in manually? Or is there a straightforward way to build armhf multiarch packages of these things to install on my host?

Thanks,

http://ports.ubuntu.com/pool/main/liba/libao/libao-dev_1.1.0-2ubuntu1_armhf.deb

Looks like for libmpg123 your on your own..

Regards,

Hmm. I must be missing some config somewhere, I don't see that.

$ aptitude search libao
i A libao-common - Cross Platform Audio Output Library (Common files)
v libao-common:i386 -
v libao-common:armhf -
p libao-dbg - Cross Platform Audio Output Library Debug Symbols
p libao-dbg:i386 - Cross Platform Audio Output Library Debug Symbols
i libao-dev - Cross Platform Audio Output Library Development
p libao-dev:i386 - Cross Platform Audio Output Library Development
p libao-ocaml - OCaml bindings for libao -- runtime files
p libao-ocaml:i386 - OCaml bindings for libao -- runtime files
v libao-ocaml-1zwf3:i386 -
p libao-ocaml-dev - OCaml bindings for libao -- development files
p libao-ocaml-dev:i386 - OCaml bindings for libao -- development files
v libao-ocaml-dev-1zwf3:i386 -
v libao-ocaml-dev-it4j5 -
v libao-ocaml-it4j5 -
i A libao4 - Cross Platform Audio Output Library
p libao4:i386 - Cross Platform Audio Output Library
p libaopalliance-java - library for interoperability for Java AOP implementations
p libaopalliance-java-doc - library for interoperability for Java AOP implementations - documentation
p libaosd-dev - atheme.org's on screen display library - dev
p libaosd-dev:i386 - atheme.org's on screen display library - dev
p libaosd-text2 - atheme.org's on screen display library - text layout
p libaosd-text2:i386 - atheme.org's on screen display library - text layout
p libaosd2 - atheme.org's on screen display library - main
p libaosd2:i386 - atheme.org's on screen display library - main

I'm not terribly familiar with apt or dpkg; is there some kind of repo I need to add?

Thanks,
Rick