gradle : How to run externalNativeBuildDebug task after a custom task

I am working on Android project which uses build.gradle. I want to run externalNativeBuildDebug task after a custom task.

In build.gradle, I specify:

task mytask()
{
    println 'hello'
}


tasks.getByName("externalNativeBuildDebug").mustRunAfter(mytask)

But gradle throws this error :

Task with name 'externalNativeBuildDebug' not found in project ':app'.

I have defined externalNativeBuild block in android{} block

externalNativeBuild {
            cmake {
                path file('CMakeLists.txt')
                version '3.18.1'
            }
        }

Is there a way to get externalNativeBuildDebug task and set its dependency?