[clang] [llvm] [DirectX] Add target builtins (PR #134439)

[Farzon Lotfi via llvm-commits]

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+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
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farzonl wrote:

No this is a c only test. Since we are exposing the backend api as a target any frontend is technically suppose to be able to access it. This test is to confirm that we aren't gating the directX backend.

https://github.com/llvm/llvm-project/pull/134439