Compiler flags in vscode with nRF connecy extension

[AndyM]

I want to add compiler  flags to my  build configuration i.e _DEBUG, etc

My understanding is that  a build is done by  build task

nRF Connect extension allows to create a tasks.json from a default nRF Connect build task

In  Terminal->Configure tasks I can select nrf Connect build and it creates the following tasks.json file

{

    "version": "2.0.0",

    "tasks": [

        {

           

            "type": "nrf-connect-build",

            "config": "c:\\<project>\\build",

            "runCmake": false,

            "problemMatcher": [

                "$gcc",

                "$cmake",

                "$kconfig",

                "$kconfig_syntax",

                "$kconfig_syntax_files",

                "$dts",

                "$dts_syntax"

            ],

            "group": "build",

            "label": "My app(Debug)"

        }

    ]

}
The problem is that I cannot add the "args" property - at least in other discussions I saw it being used to add compiler flags 

When I add it I get an error "args is not allowed"
How can I add compile flags to my nrf connect build task ? Or is there another way to do this?

My ultimate goal is to create a debug and release configurations with some defines present in one but not the other 

Thanks

[AndyM]

Did a bit more experimentation. The only way I could make this work was to add the following to CMakeLists.txt
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DAPP_DBG_LEVEL=4")
But that does achieve my goal of setting that flag to a certain value based on a condition ( debug vs release build )
When I set that flag in the build configuration window "Extra flags for CMAKE" I see it appear in the output but the flag is not processed by the preprocessor so it remains undefined in the code
#ifndef APP_DBG_LEVEL
#error App debug level undefined
#endif