fno-char8_t argument is ignored from compile commands

[BluTree]

Environment

• OS and Version: W11 22631.4460
• VS Code Version: 1.95.1
• C/C++ Extension Version: 1.23.1

Bug Summary and Steps to Reproduce

Bug Summary:
An option exists on clang (there is an equivalent on msvc with /Zc:char8_t-) removing the char8_t type from the language in C++20. It is controlled in clang by the -fno-char8_t argument.
When using compile commands, with this argument and --std=c++20 present in the command, the parsing seems to ignore the -fno-char8_t, leading to Intellisense errors.

When looking for duplicates, I found #12106, but given the explanation, it seems that every argument is parsed, even if not needed so it doesn't related to this issue.

Steps to reproduce:

1. create a file containing the code below:

#include <stdio.h>

int main(int argc, char** argv)
{
	printf(u8"Hello UTF-8");

	return 0;
}

2. create a compile commands containing the source with both -fno-char8_t and --std=c++20 in the command, as below:

[
	{
		"directory": "src",
		"command": "clang++ -g -Wall -fno-char8_t --std=c++20",
		"file": "test.cc"
	}
]

3. Notice the errors displaying on u8, indicating that argument const char8_t* is incompatible with const char*

Expected behavior:
The parsing should take account of the -fno-char8_t to give it correctly to the parser. On a side note, the argument is not given either to clang-tidy, leading to other errors related to it.

Configuration and Logs

-------- Diagnostics - 11/15/2024, 11:10:57 PM
Version: 1.23.1
Current Configuration:
{
    "name": "Win32",
    "includePath": [
        "c:/Dev/Sources/C++ tests/**"
    ],
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "cStandard": "c17",
    "intelliSenseMode": "windows-clang-x64",
    "compileCommands": "c:\\Dev\\Sources\\C++ tests/compile_commands.json",
    "compilerPathIsExplicit": false,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "intelliSenseModeIsExplicit": true,
    "compileCommandsInCppPropertiesJson": "${workspaceFolder}/compile_commands.json",
    "cppStandard": "c++17",
    "mergeConfigurations": false,
    "browse": {
        "path": [
            "c:/Dev/Sources/C++ tests/**",
            "${workspaceFolder}"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
Modified Settings:
{
    "C_Cpp.default.compilerPath": "C:\\Dev\\LLVM\\bin\\clang.exe",
    "C_Cpp.default.cppStandard": "c++17",
    "C_Cpp.exclusionPolicy": "checkFilesAndFolders",
    "C_Cpp.formatting": "clangFormat",
    "C_Cpp.doxygen.generateOnType": false,
    "C_Cpp.codeAnalysis.exclude": {
        "folder": true
    },
    "C_Cpp.codeAnalysis.clangTidy.enabled": true,
    "C_Cpp.codeAnalysis.clangTidy.path": "C:\\Dev\\LLVM\\bin\\clang-tidy.exe",
    "C_Cpp.intelliSenseMemoryLimit": 16384,
    "C_Cpp.loggingLevel": "Debug",
    "C_Cpp.experimentalFeatures": "enabled"
}
Additional Tracked Settings:
{
    "editorTabSize": 4,
    "editorInsertSpaces": false,
    "editorAutoClosingBrackets": "languageDefined",
    "filesEncoding": "utf8",
    "filesAssociations": {
        "*.sln": "xml",
        "log": "log"
    },
    "filesExclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": true,
        "**/CVS": true,
        "**/.DS_Store": true,
        "**/Thumbs.db": true
    },
    "filesAutoSaveAfterDelay": false,
    "editorInlayHintsEnabled": true,
    "editorParameterHintsEnabled": true,
    "searchExclude": {
        "**/node_modules": true,
        "**/bower_components": true,
        "**/*.code-search": true
    },
    "workbenchSettingsEditor": "ui"
}
cpptools version (native): 1.23.1.0
Current database path: C:\USERS\AUBIN\APPDATA\LOCAL\MICROSOFT\VSCODE-CPPTOOLS\2E0838E3C682A3A1661B48151AF947FF\.BROWSE.VC.DB
Translation Unit Mappings:
[ C:\Dev\Sources\C++ tests\src\test.cc - source TU]:
Translation Unit Configurations:
[ C:\Dev\Sources\C++ tests\src\test.cc ]
    Process ID: 17732
    Memory Usage: 64 MB
    Compiler Path: C:\Dev\LLVM\bin\clang++.exe
    Includes:
    System Includes:
        C:\Dev\LLVM\lib\clang\18\include
        C:\Dev\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.41.34120\include
        C:\Dev\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.41.34120\atlmfc\include
        C:\Windows Kits\10\Include\10.0.22621.0\ucrt
        C:\Windows Kits\10\Include\10.0.22621.0\shared
        C:\Windows Kits\10\Include\10.0.22621.0\um
        C:\Windows Kits\10\Include\10.0.22621.0\winrt
        C:\Windows Kits\10\Include\10.0.22621.0\cppwinrt
    Standard Version: c++20
    IntelliSense Mode: windows-clang-x64
    Other Flags:
        --clang
        --clang_version=180108
        --ms_compatibility
    compile_commands.json entry:
        directory: c:\Dev\Sources\C++ tests/src
        file: c:\Dev\Sources\C++ tests/src/test.cc
        command: clang++ -g -Wall -fno-char8_t --std=c++20
Total Memory Usage: 64 MB
Browse Paths from compile_commands.json, from workspace folder: C:\Dev\Sources\C++ tests
    C:\Dev\Sources\C++ tests\src

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 5383

Other Extensions

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Additional context

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