t/.deps are files created at compile-time iff certain libtool options are enabled, and contain data highly specific to the local build machine. Therefore, they should not be included in a source release. I'm not sure if there is a 'make distclean' or similar target that has a bug, or some manual intervention was not documented or performed correctly, but libmaxminddb-1.3.2.tar.gz has t/.deps/*.Po that point to linux headers in /usr/include, which is definitely not correct for my darwin (OS X) machine.