Upgrade to Scala.js 1.20.1.

In this commit, we ignore the new test for `linkTimeIf`.

Author: sjrd

project/Build.scala

@@ -2820,6 +2820,7 @@ object Build {
           ++ (dir / "js/src/test/scala" ** (("*.scala": FileFilter)
             -- "StackTraceTest.scala" // would require `npm install source-map-support`
             -- "UnionTypeTest.scala" // requires the Scala 2 macro defined in Typechecking*.scala
+            -- "LinkTimeIfTest.scala" // TODO implement support for linkTimeIf
             )).get
 
           ++ (dir / "js/src/test/require-2.12" ** "*.scala").get

project/ScalaLibraryPlugin.scala

@@ -6,13 +6,13 @@ import scala.jdk.CollectionConverters.*
 import java.nio.file.Files
 import xsbti.VirtualFileRef
 import sbt.internal.inc.Stamper
+import org.scalajs.sbtplugin.ScalaJSPlugin.autoImport.scalaJSVersion
 
 object ScalaLibraryPlugin extends AutoPlugin {
 
   override def trigger = noTrigger
 
-  private val scala2Version  = "2.13.16"
-  private val scalaJSVersion = "1.19.0"
+  private val scala2Version = "2.13.16"
 
   val fetchScala2ClassFiles = taskKey[(Set[File], File)]("Fetch the files to use that were compiled with Scala 2")
   val fetchScala2SJSIR = taskKey[(Set[File], File)]("Fetch the .sjsir to use from Scala 2")

project/plugins.sbt

@@ -6,7 +6,7 @@
 libraryDependencySchemes +=
   "org.scala-lang.modules" %% "scala-xml" % VersionScheme.Always
 
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.19.0")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.1")
 
 addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.2.1")