scala-js 0.6.23. fix warnings

Author: xuwei-k

Diff for: build.sbt

@@ -1,4 +1,5 @@
 import ScalaModulePlugin._
+import sbtcrossproject.crossProject
 
 scalaVersionsByJvm in ThisBuild := {
   val v211 = "2.11.12"
@@ -15,7 +16,7 @@ lazy val root = project.in(file("."))
   .aggregate(xmlJS, xmlJVM)
   .settings(disablePublishing)
 
-lazy val xml = crossProject.in(file("."))
+lazy val xml = crossProject(JSPlatform, JVMPlatform).in(file("."))
   .settings(scalaModuleSettings)
   .jvmSettings(scalaModuleSettingsJVM)
   .settings(

Diff for: project/plugins.sbt

@@ -1,3 +1,5 @@
 addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module" % "1.0.14")
 
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.22")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.23")
+
+addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "0.4.0")