run.sh dies on OSX

Created originally on Bitbucket by pnathan (Paul Nathan)

OSX mktemp takes different options than Linux mktemp.

Executing bash -x run.sh gives this error:

++ mktemp
usage: mktemp [-d] [-q] [-t prefix] [-u] template ...
       mktemp [-d] [-q] [-u] -t prefix 

Further:

readlink -f <file>

is a Linux option. This also causes pain.

Further: GNU sed takes -r, BSD sed does not.