SBT: How to define dependencies of subprojects in subprojects' build.sbt files?

Question

The following build.sbt file works, but it defines the dependencies of all subprojects:

name := "myproject"

version := "1.0"

scalaVersion := "2.11.8"

libraryDependencies ++= Seq(
  "org.scalafx" %% "scalafx" % "8.0.60-R9"
)


lazy val aLib = (project in file("lib/a"))
lazy val bLib = (project in file("lib/b"))
  .dependsOn(aLib)
  .dependsOn(cLib)
lazy val cLib = (project in file("lib/c"))
  .dependsOn(aLib)
lazy val myApp = (project in file("myapp"))
  .dependsOn(aLib)
  .dependsOn(bLib)
  .dependsOn(cLib)
  .aggregate(aLib, bLib, cLib)

Since each subproject (directories lib/a, lib/b, lib/c, myapp) has its own build.sbt file, I would like to use those build files to define the individual dependencies of each project.

I tried to move the dependsOn/aggregate statements to the subprojects' build files, but I am not able to make it work that way. What is the recommended way?