Override default includePath for intelliSense in vscode C/C++

I am trying to configure vscode intellisense for a C project where I have a custom compiler which is using his "own" implementation of the standard lib (optimized for the targeted processor).

I can succesfully include project libraries, e.g. #include <gpio.h> refers to the correct specific implementation of the project.

But in the case of let's say #include <string.h> intellisense is pointing to my standard windows install (C:\Program Files (x86)\Windows Kits\10\Include\10.0.18362.0\ucrt\string.h) and not to the desired one who should be in my case in C:/MWLite/MetaWare/arc/libs/inc/string.h

I included the path in c_cpp_properties.json:

{
    "name": "arc",
    "includePath": [
        "${workspaceFolder}/**",
        "C:/MWLite/MetaWare/arc/**"
    ],
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "compilerPath": "C:/MWLite/MetaWare/arc/bin/gmake.exe",
    "cStandard": "c11",
    "cppStandard": "c++17",
    "intelliSenseMode": "gcc-x64"
}

How can I "force" intellisense to look first in the specified path for libc?