This script simply installs cross compilers for multiple plateform (linux, freebsd, openbsd, netbsd, dragonfly, darwin) and multiple architectures (32 and 64 bits).
This scripts requires gvm to be installed. However, the authors seem to not care anymore about pull requests and Go 1.4 does not work due to some changes in the source organization. You have to apply this patch.
Package genmd5 generates MD5 sums from parsers archives, suitable to generate the MD5SUM file for the parsers repository. This tool is useful because the output of standard tools to generate MD5 sums may vary especially md5sum(1) from Linux and md5i(1) from the BSDs.