[XRay] Change std::sort to llvm::sort in response to r327219
[XRay] Change std::sort to llvm::sort in response to r327219

r327219 added wrappers to std::sort which randomly shuffle the container before
sorting.  This will help in uncovering non-determinism caused due to undefined
sorting order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of
std::sort.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@330561 91177308-0d34-0410-b5e6-96231b3b80d8

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