From XastirWiki
Xastir compiles cleanly on Mac OS X. The Xcode and X11SDK development tools are required. These are free from Apple, and could be on an installation disc that came with your Mac.
Some of the support packages do not compile so cleanly. Dana N1OFZ has documented some problems and provided some workarounds here: http://n1ofz.connares.org/software/Xastir_old