Access out of scope fix in OCLToSPIRVBase::visitCallAtomicCmpXchg (#2264)

Pointer named Expected was taken by reference to closure to be executed
later by Mutator. Mutator executes the closure in his destructor
which happens after the destruction of Expected pointer stack frame.
This fix clears some ASan errors from #2233.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@c7cd904

Author: bwlodarcz

llvm-spirv/lib/SPIRV/OCLToSPIRV.cpp

@@ -485,11 +485,12 @@ CallInst *OCLToSPIRVBase::visitCallAtomicCmpXchg(CallInst *CI) {
     Mutator.mapArg(1, [=](IRBuilder<> &Builder, Value *V) {
       return Builder.CreateLoad(MemTy, V, "exp");
     });
-    Mutator.changeReturnType(MemTy, [&](IRBuilder<> &Builder, CallInst *NCI) {
-      NewCI = NCI;
-      Builder.CreateStore(NCI, Expected);
-      return Builder.CreateICmpEQ(NCI, NCI->getArgOperand(1));
-    });
+    Mutator.changeReturnType(
+        MemTy, [Expected, &NewCI](IRBuilder<> &Builder, CallInst *NCI) {
+          NewCI = NCI;
+          Builder.CreateStore(NCI, Expected);
+          return Builder.CreateICmpEQ(NCI, NCI->getArgOperand(1));
+        });
   }
   return NewCI;
 }