Type: LanguageService

Describe the bug
When I change intellisense default mode, it seems that some settings are mixed up and show different values when setting some values. I happened to fond this when it was showing VLA intellisense errors on a C18 standard when it sohuldn't in clang on windows.

• OS and Version: Windows 10
• VS Code Version: 1.48.2
• C/C++ Extension Version: 0.30.0-insiders4
• Other extensions you installed (and if the issue persists after disabling them): I do have CodeLLDB 1.5.3, but the issue seems to be not related to this extension.

Steps to reproduce

1. Go to settings.json
2. Set the C_Cpp.default.intelliSenseMode value to anything you want to.
3. Call the C/C++ diagnostics. Look for the IntelliSense Mode log file.
4. See mixed up versions. This will also trigger errors given the intelligence (for example VLAs)
   a. clang-x86 and clang-x64 results in msvc-x86 and msvc-x64
   b. gcc-x86 and gcc-x64 results in clang-x86 and clang-x64
   c. gcc-arm results in clang-arm

The rest of the settings work fine.

This also happens if you set this values via the UI method. When I reload the project, the feature seems to correct itself, up until I close the settings window or file.

Expected behavior
Have correct relations to the settings.