Compiler options for compile server

Hi all,

how can I set the scala compiler options (such as -feature) when using the compile server in external build mode?
Compiler > Scala Compiler in Settings > Project Settings is disabled while using the compile server

Also, scalacOptions in build.sbt seems to be ignored (I don't know if this is expected; I know that the compiler server is using the SBT infrastructure)

thanks in advance
Francesco