Silence deprecations about AnyRefMap in scalajs-ir.

Author: sjrd

project/Build.scala

@@ -739,6 +739,13 @@ object Build {
       // Use source 3.3 to avoid fatal migration warnings on scalajs-ir
       scalacOptions ++= Seq("-source", "3.3"),
 
+      /* Ignore a deprecation warning about AnyRefMap in scalajs-ir. The latter
+       * cross-compiles for 2.12, and therefore AnyRefMap remains useful there
+       * for performance reasons.
+       * The build of Scala.js core does the same thing.
+       */
+      scalacOptions += "-Wconf:cat=deprecation&origin=scala\\.collection\\.mutable\\.AnyRefMap.*:s",
+
       // Generate compiler.properties, used by sbt
       (Compile / resourceGenerators) += Def.task {
         import java.util._