-lrt is not needed in OpenBSD.

clock_gettime is in libc in OpenBSD. [1]

[1] http://www.openbsd.org/cgi-bin/cvsweb/ports/devel/ruby-prof/patches/patch-ext_ruby_prof_extconf_rb?rev=1.1
Merge pull request #119 from edogawaconan/openbsd

-lrt is not needed in OpenBSD.
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Merge pull request #125 from utenmiki/master

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Specify version of minitest. Tests do not run on 2.0 otherwise.
Merge pull request #126 from agrimm/get_tests_running

Specify version of minitest. Tests do not run on 2.0 otherwise.