Atlas aborts the build some kind of CPU frequency scaling is detected on the

build machine because that feature offsets the performance timings. We ignore
that check, however, because with binaries being pre-built on Hydra those
timings aren't accurate for the local machine in the first place. The build log
might show something such as the following:

 | It appears you have cpu throttling enabled, which makes timings
 | unreliable and an ATLAS install nonsensical.  Aborting.
 | See ATLAS/INSTALL.txt for further information
 | Ignoring CPU throttling by user override!

svn path=/nixpkgs/trunk/; revision=32506