HA: merge-string.s test failing on windows

[George Rimar via llvm-commits]

>>That test is not failing on my Windows box (MSVC 2013 64-bit), so I have no idea why that's failing on your machine.
>
>Ok, I`ll investigate it then.
>I am running on MSVC 2015 community edition.

I guess buildbots run 2013 too. At least that was told here http://reviews.llvm.org/D13203#257590
And probably there is some difference in behavior, not sure.