Switch nd4j runtime according to setting key

Author: Atry

benchmarks/build.sbt

@@ -2,9 +2,13 @@ enablePlugins(JmhPlugin)
 
 libraryDependencies += "org.nd4j" % "nd4j-api" % "0.8.0"
 
-libraryDependencies += "org.nd4j" % "nd4j-cuda-8.0-platform" % "0.8.0"
+val nd4jRuntime = settingKey[String]("\"cuda-8.0\" to run benchmark on GPU, \"native\" to run benchmark on CPU.")
 
-libraryDependencies += "org.nd4j" % "nd4j-native-platform" % "0.8.0"
+nd4jRuntime in Global := "native"
+
+libraryDependencies += {
+  "org.nd4j" % s"nd4j-${nd4jRuntime.value}-platform" % "0.8.0"
+}
 
 libraryDependencies += ("org.lwjgl" % "lwjgl" % "3.1.6").jar().classifier {
   import scala.util.Properties._