Corrected mktemp(1) for OSX

The linux and osx version of mktemp do not work the same. OSX requires
a template string passed.

    emopop:~% mktemp -d
    usage: mktemp [-d] [-q] [-t prefix] [-u] template ...
           mktemp [-d] [-q] [-u] -t prefix
    emopop:~% mktemp -d -t 'foo'
    /var/folders/7l/cxk0c90d16j0m6spkw74kpx40000gp/T/foo.qJ0FRoqM