[CodeLayout] Update to resolve Wdangling warning.

Change cc2fbc64 introduced -Wdangling
warning, use temporaries to resolve.

llvm/lib/Transforms/Utils/CodeLayout.cpp:764:27: error: temporary whose address is used as value of local variable '[minDensity, maxDensity]' will be destroyed at the end of the full-expression [-Werror,-Wdangling]
  764 |               std::minmax(ChainPred->density(), ChainSucc->density());

llvm/lib/Transforms/Utils/CodeLayout.cpp:764:49: error: temporary whose address is used as value of local variable '[minDensity, maxDensity]' will be destroyed at the end of the full-expression [-Werror,-Wdangling]
  764 |               std::minmax(ChainPred->density(), ChainSucc->density());