I'd check ./configure --help|less and try to find if there's anything related to ALSA.
There is and it's exactly that, the files are all there it's just that configure accepts --enable-libsalsa=NO just fine but not --enable-libsalsa=YES.
Later I'll try to manually compile it instead of using a modified pkgbuild. But even if I can compile it, it doesn't mean it will work. It was not made to be a perfect alsa emulation/translation layer after all.
Guys, just point libasound to use OSS. It works a lot better than either systems' emulation.