Test that IDE can be started in CI, upgrade ref compiler

dotty-library-bootstrappedJS scalacOptions handling was broken, I fixed
it by upgrading the reference compiler to simplify the handling of
-Yerased-terms, but I also removed all scalajs projects from IDE startup
as explained in the comment.

Author: smarter

.drone.yml

@@ -40,7 +40,7 @@ steps:
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/2/ && cd /tmp/2/
-  - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test ;dotty-staging/test ;sjsSandbox/run;sjsSandbox/test;sjsJUnitTests/test"
+  - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test ;dotty-staging/test ;sjsSandbox/run;sjsSandbox/test;sjsJUnitTests/test ;configureIDE"
   - ./project/scripts/bootstrapCmdTests
 
 - name: community_build

project/Build.scala

@@ -54,11 +54,15 @@ object MyScalaJSPlugin extends AutoPlugin {
 
     // Typecheck the Scala.js IR found on the classpath
     scalaJSLinkerConfig ~= (_.withCheckIR(true)),
+
+    // Exclude all these projects from `configureIDE/launchIDE` since they
+    // take time to compile, print a bunch of warnings, and are rarely edited.
+    excludeFromIDE := true
   )
 }
 
 object Build {
-  val referenceVersion = "0.21.0-RC1"
+  val referenceVersion = "0.22.0-bin-20200114-193f7de-NIGHTLY"
 
   val baseVersion = "0.22.0"
   val baseSbtDottyVersion = "0.3.5"
@@ -730,16 +734,18 @@ object Build {
     case Bootstrapped => `dotty-compiler-bootstrapped`
   }
 
-  // Settings shared between dotty-library and dotty-library-bootstrapped
+  // Settings shared between dotty-library, dotty-library-bootstrapped and dotty-library-bootstrappedJS
   lazy val dottyLibrarySettings = Seq(
-    // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
-    scalacOptions in Compile ++= Seq("-sourcepath", (sourceDirectories in Compile).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator)),
+    scalacOptions in Compile ++= Seq(
+      // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
+      "-sourcepath", (sourceDirectories in Compile).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator),
+     // support declaration of scala.compiletime.erasedValue
+      "-Yerased-terms"
+    ),
   )
 
   lazy val `dotty-library` = project.in(file("library")).asDottyLibrary(NonBootstrapped)
   lazy val `dotty-library-bootstrapped`: Project = project.in(file("library")).asDottyLibrary(Bootstrapped)
-    // TODO: move -Yerased-terms to dottyLibrarySettings on reference compiler update
-    .settings(scalacOptions in Compile += "-Yerased-terms") // support declaration of scala.compiletime.erasedValue
 
   def dottyLibrary(implicit mode: Mode): Project = mode match {
     case NonBootstrapped => `dotty-library`
@@ -761,7 +767,6 @@ object Build {
     settings(
       unmanagedSourceDirectories in Compile :=
         (unmanagedSourceDirectories in (`dotty-library-bootstrapped`, Compile)).value,
-      scalacOptions += "-Yerased-terms", // support declaration of scala.compiletime.erasedValue
     )
 
   lazy val tastyCoreSettings = Seq(