No, you do not modify buildscript in your convention plugin.
Your convention plugin is built in an own build.
This build has an own build script.
In that build script you define that your plugin code has a dependency on the AGP.
No, you do not modify buildscript in your convention plugin.
Your convention plugin is built in an own build.
This build has an own build script.
In that build script you define that your plugin code has a dependency on the AGP.