fix(llvm) Improve runenvs for llvm and clang toolchain

[Arthapz]

This PR enable the usage of sanitizers on windows without manual DLL copy or PATH setting with llvm and clang toolchains

[gemini-code-assist]

Summary of Changes

Hello @Arthapz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses critical linking issues for LLVM-based projects on Windows, specifically concerning compiler-rt builtins and libc++ libraries. It introduces robust mechanisms for xmake to correctly locate and link these components, ensuring proper compilation and execution. A new dedicated test case has been added to validate these fixes.

Highlights

• New LLVM Compiler-RT Test: A new test project llvm_compiler_rt has been added, including main.c which uses __int128 to verify compiler-rt builtins, and test.lua to automate its build and execution with the LLVM toolchain on xmake.
• Enhanced LLVM Path Detection: New functions like _get_llvm_resourcedir and _get_llvm_compiler_win_rtdir_and_link were introduced in xmake/modules/core/tools/clang.lua to improve the detection of LLVM's resource, root, and compiler-rt library directories, particularly for Windows environments.
• Explicit Windows LLVM Linker Fixes: The nf_runtime function in xmake/modules/core/tools/clang.lua now explicitly manages libc++ include paths and forces the linking of compiler-rt builtins on Windows, addressing known issues with automatic linking in LLVM on this platform.
• Expanded Compiler Runtime Tool Support: The compiler_runtime rule in xmake/rules/utils/compiler_runtime/xmake.lua has been updated to recognize clang as a valid compiler when determining and applying default Visual Studio runtimes on Windows.

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[gemini-code-assist]

Code Review

This pull request effectively addresses the issue of linking LLVM compiler runtime builtins on Windows. The changes are well-structured, introducing a new test case to validate the fix and refactoring the LLVM path discovery logic for better clarity and maintainability. The core of the fix, which involves correctly identifying the compiler-rt library and passing the necessary flags to the compiler and linker, appears to be sound. I've added a couple of minor comments regarding code style and indentation to align with the project's conventions.