Fix Windows Clang compiler flags in CMake configuration

[justinzhuguangwen]

Description

This PR fixes Windows build compatibility issues when using Clang as the compiler on Windows (with the MSVC toolchain). The build system was previously attempting to use Linux-specific compiler and linker flags that are not supported on Windows, causing build failures or warnings. This change adds conditional logic to use platform-appropriate flags based on the target platform.

Context:
When Clang is used on Windows (not MSVC compiler, but Clang with MSVC toolchain), it has different capabilities and limitations compared to Clang on Linux. The previous code assumed a Linux-like environment, which caused issues on Windows.

Key Changes:

1. DEF File Format Handling (lines 41-48):

   • On Windows, use Windows .def file format via CMAKE_LINK_DEF_FILE_FLAG instead of Linux version-script format
   • Use win${TBB_ARCH} prefix for Windows DEF files instead of lin${TBB_ARCH}
   • Maintains backward compatibility for non-Windows platforms

2. Compile Flags (lines 72-78):

   • Excludes -fPIC on Windows (not supported by Clang with MSVC toolchain)
   • Excludes -fstack-clash-protection and -fcf-protection on Windows (not supported)
   • Adds -D_CRT_SECURE_NO_WARNINGS to suppress CRT security warnings for deprecated functions (e.g., getenv, strncpy) that TBB uses
   • Retains -fstack-protector-strong and format security checks on Windows

3. Library Compile Flags (line 80):

   • Explicitly excludes Windows from -fstack-clash-protection and -fcf-protection=full flags
   • These flags are only applied on non-Apple, non-Android, x86/x64 platforms that are not Windows

4. Linker Flags (lines 84-88):

   • Excludes Windows from -z linker options (relro, now, noexecstack)
   • These options are Linux-specific and not supported by lld-link on Windows
   • Updated comments to clarify that -z switch is not supported on both macOS and Windows

Impact:

• ✅ Windows builds with Clang (MSVC toolchain) now succeed without unsupported flag errors
• ✅ Proper Windows .def file format is used instead of Linux version-script
• ✅ CRT security warnings are suppressed for deprecated functions that TBB uses
• ✅ No impact on Linux, macOS, or other platforms (backward compatible)

Fixes # - issue number(s) if exists

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• bug fix - change that fixes an issue
• new feature - change that adds functionality
• tests - change in tests
• infrastructure - change in infrastructure and CI
• documentation - documentation update

Tests

• added - required for new features and some bug fixes
• not needed

Documentation

• updated in # - add PR number
• needs to be updated
• not needed

Breaks backward compatibility

• Yes
• No
• Unknown

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Other information

Testing:

• ✅ Verified that the changes maintain existing behavior on Linux and macOS
• ✅ Tested that Windows builds with Clang (MSVC toolchain) now succeed without unsupported flag errors
• ✅ Confirmed that Windows-specific DEF file format is correctly used
• ✅ Verified that all conditional branches work correctly for their respective platforms

Technical Details:

• The changes use WIN32 CMake variable to detect Windows platform (works for both native Windows and cross-compilation)
• Windows-specific flags are only applied when WIN32 is true, ensuring other platforms are unaffected
• The -z linker options are Linux ELF-specific and not supported by lld-link on Windows
• -fPIC is not needed on Windows as DLLs use a different linking model