Use the standard crossProject builder.

Instead of the `CrossProject.apply` method. This is mostly so that
we do not need to explicitly `import` anything, in order to be
source compatible with Scala.js 1.0.0-M1.

Author: sjrd

.travis.yml

@@ -1,10 +1,10 @@
 sudo: false
 language: scala
 script:
-  - sbt ++$TRAVIS_SCALA_VERSION root/scalastyle testSuiteJVM/scalastyle testSuiteJVM/test:scalastyle testSuite/scalastyle testSuite/test:scalastyle
+  - sbt ++$TRAVIS_SCALA_VERSION root/scalastyle testSuiteJVM/scalastyle testSuiteJVM/test:scalastyle testSuiteJS/scalastyle testSuiteJS/test:scalastyle
   - sbt ++$TRAVIS_SCALA_VERSION testSuiteJVM/test
-  - sbt ++$TRAVIS_SCALA_VERSION testSuite/test
-  - sbt ++$TRAVIS_SCALA_VERSION 'set scalaJSStage in Global := FullOptStage' testSuite/test
+  - sbt ++$TRAVIS_SCALA_VERSION testSuiteJS/test
+  - sbt ++$TRAVIS_SCALA_VERSION 'set scalaJSStage in Global := FullOptStage' testSuiteJS/test
   - sbt ++$TRAVIS_SCALA_VERSION publishLocal
 scala:
   - 2.10.6

build.sbt

@@ -1,6 +1,3 @@
-import sbt.Keys._
-import org.scalajs.sbtplugin.cross.CrossProject
-
 crossScalaVersions in ThisBuild := Seq("2.11.11", "2.10.6", "2.12.2", "2.13.0-M1")
 scalaVersion in ThisBuild := (crossScalaVersions in ThisBuild).value.head
 
@@ -59,12 +56,7 @@ lazy val root: Project = project.in(file(".")).
     pomIncludeRepository := { _ => false }
   )
 
-lazy val testSuite = CrossProject(
-  jvmId = "testSuiteJVM",
-  jsId = "testSuite",
-  base = file("testSuite"),
-  crossType = CrossType.Full
-).
+lazy val testSuite = crossProject.
   jsConfigure(_ .enablePlugins(ScalaJSJUnitPlugin)).
   settings(commonSettings: _*).
   settings(