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

[mgrang]

Summary

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.

Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer the comments section in D44363 for a list of all the required patches.

[RKSimon]

SGTM but @sunfish should have the final say.

[mgrang]

Ping for reviews please.

[sunfish]

LGTM.

llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp

for (unsigned i = 0; i < NumVRegs; ++i) {
     SortedIntervals.push_back(LI);
   }
   DEBUG(dbgs() << '\n');
 
   // Sort them to put arguments first (since we don't want to rename live-in
   // registers), by weight next, and then by position.
   // TODO: Investigate more intelligent sorting heuristics. For starters, we
   // should try to coalesce adjacent live intervals before non-adjacent ones.
-  std::sort(SortedIntervals.begin(), SortedIntervals.end(),
+  llvm::sort(SortedIntervals.begin(), SortedIntervals.end(),
              [MRI](LiveInterval *LHS, LiveInterval *RHS) {
                if (MRI->isLiveIn(LHS->reg) != MRI->isLiveIn(RHS->reg))
                  return MRI->isLiveIn(LHS->reg);
                if (LHS->weight != RHS->weight)
                  return LHS->weight > RHS->weight;
                if (LHS->empty() || RHS->empty())
                  return !LHS->empty() && RHS->empty();
                return *LHS < *RHS;
              });
 
   DEBUG(dbgs() << "Coloring register intervals:\n");
   SmallVector<unsigned, 16> SlotMapping(SortedIntervals.size(), -1u);
   SmallVector<SmallVector<LiveInterval *, 4>, 16> Assignments(
       SortedIntervals.size());
   BitVector UsedColors(SortedIntervals.size());
   bool Changed = false;
   for (size_t i = 0, e = SortedIntervals.size(); i < e; ++i) {