[ValueTracking] Avoid undefined behavior in unittest by not making a named ArrayRef from a std::initializer_list

[craig.topper]

Summary

One of the ValueTracking unittests creates a named ArrayRef initialized by a std::initializer_list. The underlying array for an std::initializer_list is only guaranteed to have a lifetime as long as the initializer_list object itself. So this can leave the ArrayRef pointing at an array that no long exists.

This fixes this to just create an explicit array instead of an ArrayRef.

[sanjoy]

I think used the ArrayRef to make sure we range check the accesses, but that's probably redundant since we have sanitizer builds running regularly.

llvm/trunk/unittests/Analysis/ValueTrackingTest.cpp

TEST(ValueTracking, GuaranteedToTransferExecutionToSuccessor) {
   SMDiagnostic Error;
   auto M = parseAssemblyString(Assembly, Error, Context);
   assert(M && "Bad assembly?");
 
   auto *F = M->getFunction("f");
   assert(F && "Bad assembly?");
 
   auto &BB = F->getEntryBlock();
-  ArrayRef<bool> ExpectedAnswers = {
+  bool ExpectedAnswers[] = {
       true,  // call void @nounwind_readonly(i32* %p)
       true,  // call void @nounwind_argmemonly(i32* %p)
       false, // call void @throws_but_readonly(i32* %p)
       false, // call void @throws_but_argmemonly(i32* %p)
       true,  // call void @unknown(i32* %p) nounwind readonly
       true,  // call void @unknown(i32* %p) nounwind argmemonly
       false, // call void @unknown(i32* %p) readonly
       false, // call void @unknown(i32* %p) argmemonly