Add dummy scala{-compiler,-reflect,p}

This is needed to make dotty-compiled projects work with sbt 0.13.13, the
other needed fix is sbt/sbt#2897

Author: smarter

project/Build.scala

@@ -559,6 +559,32 @@ object DottyInjectedPlugin extends AutoPlugin {
     ).
     settings(publishing)
 
+  // sbt >= 0.13.12 will automatically rewrite transitive dependencies on
+  // any version in any organization of scala{-library,-compiler,-reflect,p}
+  // to have organization `scalaOrganization` and version `scalaVersion`
+  // (see https://github.com/sbt/sbt/pull/2634).
+  // This means that we need to provide dummy artefacts for these projects,
+  // otherwise users will get compilation errors if they happen to transitively
+  // depend on one of these projects.
+  lazy val `scala-compiler` = project.
+    settings(
+      crossPaths := false,
+      libraryDependencies := Seq(scalaCompiler)
+    ).
+    settings(publishing)
+  lazy val `scala-reflect` = project.
+    settings(
+      crossPaths := false,
+      libraryDependencies := Seq("org.scala-lang" % "scala-reflect" % scalaVersion.value)
+    ).
+    settings(publishing)
+  lazy val `scalap` = project.
+    settings(
+      crossPaths := false,
+      libraryDependencies := Seq("org.scala-lang" % "scalap" % scalaVersion.value)
+    ).
+    settings(publishing)
+
    lazy val publishing = Seq(
      publishMavenStyle := true,
      publishArtifact := true,