cpptools does not respect freestanding environment

Environment

• OS and Version: Windows 11 Build 26020
• VS Code Version: 1.86.0-insider
• C/C++ Extension Version: v1.18.5
• If using SSH remote, specify OS of remote machine: Local machine, windows

Project is being managed through CMake with a custom toolchain using clang.exe for freestanding environment.

Bug Summary and Steps to Reproduce

Bug Summary:

Using intelliSenseMode windows-clang-x64, __STDC_HOSTED__ remains 1 despite -ffreestanding

Steps to reproduce:

1. Add -ffreestanding to compilerArgs
2. Set intelliSenseMode to windows-clang-x64 or clang-x64
3. Include <stdint.h> and open it
4. Hover on #if __STDC_HOSTED__ and notice it is set to 1

Expected behavior:

__STDC_HOSTED__ is 0

Configuration and Logs

https://pastebin.com/9bhUN0jb (Too big for github)

Other Extensions

cmake tools v1.16.32

Additional context

Freestanding project.
Efi program & standalone os kernel
Using msabi-x64, clang
Projects build and run fine, but intellisense is broken.
Clangd works out of the box (compile_commands.json)

But even after setting "compileCommands": "${workspaceFolder}/.build/compile_commands.json", cpptools extensions dont work

CMakeToolchain.txt: https://pastebin.com/ngQxWhCB

Start with the reported compilerArgs and intelliSenseMode settings, then inspect the linked CMakeToolchain.txt and compile_commands.json context. Reproduce with -ffreestanding, windows-clang-x64 or clang-x64, and <stdint.h>; done means IntelliSense reports STDC_HOSTED as 0 under the freestanding configuration.