Accesing extra properties on the settings object in projects

Now that the settings are evaluated before buildSrc in Gradle 6, I would like to set a constant in settings.gradle.kts and access it in both buildSrc and projects.

I can write

extra[“foo”] = “bar”

in settings.gradle.kts, but how do I access the value in projects?

I have found this answer from 2014:

but there seems to be no way to set extra properties on the gradle object with the Kotlin DSL.