[DirectX backend] Fix build and test error caused by out of sync with upstream change.

Fix build and test error caused by
https://github.com/llvm/llvm-project/commit/a2620e00ffa232a406de3a1d8634beeda86956fd#
and
https://github.com/llvm/llvm-project/commit/304f1d59ca41872c094def3aee0a8689df6aa398

Reviewed By: beanz

Differential Revision: https://reviews.llvm.org/D137815