[DAGCombiner] Load slicing test case: attempt to really fix the buildbots (used sse4.2 instead of avx!).

<rdar://problem/14477220>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192480 91177308-0d34-0410-b5e6-96231b3b80d8