[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-x86_64-sie-win` running on `sie-win-worker` while building `clang` at step 6 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/11529

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

```
Step 6 (build-unified-tree) failure: build (failure)
...
[921/4814] Building AttrTemplateInstantiate.inc...
[922/4814] Building X86GenExegesis.inc...
[923/4814] Building AttrParsedAttrKinds.inc...
[924/4814] Building AttrParsedAttrImpl.inc...
[925/4814] Building AttrSpellingListIndex.inc...
[926/4814] Building AttrPCHRead.inc...
[927/4814] Building AttrPCHWrite.inc...
[928/4814] Building Checkers.inc...
[929/4814] Building Nodes.inc...
[930/4814] Building BuiltinsX86.inc...
FAILED: tools/clang/include/clang/Basic/BuiltinsX86.inc 
cmd.exe /C "cd /D Z:\b\llvm-clang-x86_64-sie-win\build && Z:\b\llvm-clang-x86_64-sie-win\build\bin\clang-tblgen.exe -gen-clang-builtins -I Z:/b/llvm-clang-x86_64-sie-win/llvm-project/clang/include/clang/Basic -IZ:/b/llvm-clang-x86_64-sie-win/llvm-project/clang/include -IZ:/b/llvm-clang-x86_64-sie-win/build/tools/clang/include -IZ:/b/llvm-clang-x86_64-sie-win/build/include -IZ:/b/llvm-clang-x86_64-sie-win/llvm-project/llvm/include Z:/b/llvm-clang-x86_64-sie-win/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"
Z:/b/llvm-clang-x86_64-sie-win/llvm-project/clang/include/clang/Basic/BuiltinsX86.td:147:7: error: Unexpected header name
  def _m_prefetch : X86LibBuiltin<"void(void *)">;
      ^
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: Z:\\b\\llvm-clang-x86_64-sie-win\\build\\bin\\clang-tblgen.exe -gen-clang-builtins -I Z:/b/llvm-clang-x86_64-sie-win/llvm-project/clang/include/clang/Basic -IZ:/b/llvm-clang-x86_64-sie-win/llvm-project/clang/include -IZ:/b/llvm-clang-x86_64-sie-win/build/tools/clang/include -IZ:/b/llvm-clang-x86_64-sie-win/build/include -IZ:/b/llvm-clang-x86_64-sie-win/llvm-project/llvm/include Z:/b/llvm-clang-x86_64-sie-win/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

[931/4814] Building NodeClasses.inc...
[932/4814] Building arm_sve_sema_rangechecks.inc...
[933/4814] Building riscv_vector_builtin_sema.inc...
[934/4814] Building X86GenRegisterBank.inc...
[935/4814] Building riscv_vector_builtin_cg.inc...
[936/4814] Building X86GenRegisterInfo.inc...
[937/4814] Building RISCVTargetParserDef.inc...
[938/4814] Building X86GenAsmWriter1.inc...
[939/4814] Building X86GenMnemonicTables.inc...
[940/4814] Building X86GenAsmWriter.inc...
[941/4814] Building X86GenInstrMapping.inc...
[942/4814] Building X86GenAsmMatcher.inc...
[943/4814] Building X86GenFoldTables.inc...
[944/4814] Building X86GenDisassemblerTables.inc...
[945/4814] Building X86GenFastISel.inc...
[946/4814] Building X86GenGlobalISel.inc...
[947/4814] Building X86GenSubtargetInfo.inc...
[948/4814] Building X86GenDAGISel.inc...
[949/4814] Building X86GenInstrInfo.inc...
ninja: build stopped: subcommand failed.

```

</details>

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