A build file to show multi-project build with runtime scoped dependencies

SampleBuild.scala

import sbt._
import sbt.Keys._
import sbtassembly.Plugin._
import AssemblyKeys._

object SampleBuild extends Build {
 
  lazy val module1 = Project(
    id = "module1",
    base = file("module1"),
    settings = Project.defaultSettings ++ Seq(
      name := "module1",
      organization := "fancyOrg",
      version := "1.0",
      scalaVersion := "2.10.4",
      libraryDependencies ++= Seq("org.apache.commons" % "commons-io" % "1.3.2" % "runtime")
    )
  )

 lazy val assembly = Project(
    id = "assembly",
    base = file("assembly"),
    settings = Project.defaultSettings ++ Seq(
      name := "assembly",
      organization := "fancyOrg",
      version := "1.0",
      scalaVersion := "2.10.4"
    )
  ) dependsOn(module1 % "compile->compile;runtime->runtime") //The assembly module depending on module1 is optional 

   lazy val sample = Project(
    id = "sample",
    base = file("."),
    settings = Project.defaultSettings++ assemblySettings ++ Seq(
      name := "sample",
      organization := "fancyOrg", 
      version := "1.0",
      scalaVersion := "2.10.4"
    ) 
  ) aggregate(square,assembly) dependsOn(module1 % "compile->compile;runtime->runtime",assembly)
}