[PATCH] Fix test-release.sh to use DESTDIR

[Dan Liew]

>> For the LLVM 3.6.x tarballs the CMake files are completely missing
>> (Ubuntu tarballs). I don't understand why, the test-release.sh script
>> doesn't appear to do anything to remove these files explicitly. What
>> happened here?
>
> I'm not sure what changed between the 3.5 and 3.6 releases in this
> regard. I don't think the script itself has changed, but maybe the
> build system was changed to not generate the .cmake files in autoconf
> builds, as they would probably be broken.

Just to note Ben Pope and I figured out what was wrong. There was a
bug in the ``test-release.sh`` script
which meant the script carry on executing even if the build/tests
failed. I fixed this in r241599. In this case
the ``make install`` step was failing midway through due to the
``groff`` command not being available, the script
carried on and tarballed the partially installed files resulting in a
broken tarball.