[clang] [Win/X86] Make _m_prefetch[w] builtins to avoid winnt.h conflicts (PR #115099)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `clang` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/14019

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-unified-tree) failure: build (failure)
...
17.923 [3897/8/2078] Building AttrHasAttributeImpl.inc...
17.924 [3896/8/2079] Building CXX11AttributeInfo.inc...
17.926 [3895/8/2080] Building BuiltinsBPF.inc...
17.926 [3894/8/2081] Building Builtins.inc...
17.932 [3893/8/2082] Building BuiltinsSPIRV.inc...
17.933 [3892/8/2083] Building BuiltinsRISCV.inc...
17.937 [3891/8/2084] Building BuiltinsNVPTX.inc...
17.938 [3890/8/2085] Building BuiltinsX86_64.inc...
17.940 [3889/8/2086] Building BuiltinsHexagon.inc...
17.942 [3888/8/2087] Building BuiltinsX86.inc...
FAILED: tools/clang/include/clang/Basic/BuiltinsX86.inc /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/include/clang/Basic/BuiltinsX86.inc 
cd /Users/buildbot/buildbot-root/aarch64-darwin/build && /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/clang-tblgen -gen-clang-builtins -I /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/clang/include/clang/Basic -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/clang/include -I/Users/buildbot/buildbot-root/aarch64-darwin/build/tools/clang/include -I/Users/buildbot/buildbot-root/aarch64-darwin/build/include -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/include /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/clang/include/clang/Basic/BuiltinsX86.td --write-if-changed -o tools/clang/include/clang/Basic/BuiltinsX86.inc -d tools/clang/include/clang/Basic/BuiltinsX86.inc.d
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/clang/include/clang/Basic/BuiltinsX86.td:147:7: error: Unexpected header name
  def _m_prefetch : X86LibBuiltin<"void(void *)">;
      ^
17.945 [3888/7/2088] Building arm_fp16.inc...
17.957 [3888/6/2089] Building arm_immcheck_types.inc...
17.960 [3888/5/2090] Building arm_neon.inc...
17.961 [3888/4/2091] Building arm_mve_builtins.inc...
17.979 [3888/3/2092] Building arm_mve_builtin_cg.inc...
19.015 [3888/2/2093] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
20.249 [3888/1/2094] Building AArch64GenSubtargetInfo.inc...
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/115099