To generate the Slackware libshairport package for XBMC use:
(We assume the xbmc source is unpacked under /opt)
1. Copy the libshairport.SlacBuild file in /opt/xbmc-xx.x/lib/libshairport/
2. Copy slack-desc in /opt/xbmc-xx.x/lib/libshairport/
3. cd into /opt/xbmc-xx.x/lib/libshairport/
4. run ./libshairport.SlacBuild

The Slackware package will be generated in /tmp