Use the ordinary compiler classpath for scala-library

No longer pass `-bootclasspath /path/to/scala-library.jar` to the Scala
compiler, put the library on the ordinary classpath.

main/src/main/scala/sbt/Defaults.scala

@@ -730,14 +730,14 @@ object Defaults extends BuildCommon {
     consoleProject / scalaCompilerBridgeSource := ZincLmUtil.getDefaultBridgeSourceModule(
       appConfiguration.value.provider.scalaProvider.version
     ),
+    classpathOptions := ClasspathOptionsUtil.noboot(scalaVersion.value),
+    console / classpathOptions := ClasspathOptionsUtil.replNoboot(scalaVersion.value),
   )
   // must be a val: duplication detected by object identity
   private[this] lazy val compileBaseGlobal: Seq[Setting[_]] = globalDefaults(
     Seq(
       auxiliaryClassFiles :== Nil,
       incOptions := IncOptions.of(),
-      classpathOptions :== ClasspathOptionsUtil.boot,
-      console / classpathOptions :== ClasspathOptionsUtil.repl,
       compileOrder :== CompileOrder.Mixed,
       javacOptions :== Nil,
       scalacOptions :== Nil,

main/src/main/scala/sbt/internal/Load.scala

@@ -79,7 +79,7 @@ private[sbt] object Load {
     val dependencyResolution = IvyDependencyResolution(ivyConfiguration)
     val si = ScalaInstance(scalaProvider.version, scalaProvider.launcher)
     val zincDir = BuildPaths.getZincDirectory(state, globalBase)
-    val classpathOptions = ClasspathOptionsUtil.boot
+    val classpathOptions = ClasspathOptionsUtil.noboot(si.version)
     val scalac = ZincLmUtil.scalaCompiler(
       scalaInstance = si,
       classpathOptions = classpathOptions,

sbt-app/src/sbt-test/compiler-project/no-bootclasspath/build.sbt

@@ -0,0 +1,9 @@
+TaskKey[Unit]("check212") := checkCp(true)
+TaskKey[Unit]("check213") := checkCp(false)
+
+def checkCp(auto: Boolean) = Def.task {
+  val opts = compilers.value.scalac.classpathOptions
+  assert(opts.autoBoot == auto, opts)
+  assert(opts.filterLibrary == auto, opts)
+  ()
+}

sbt-app/src/sbt-test/compiler-project/no-bootclasspath/test

@@ -0,0 +1,4 @@
+> set scalaVersion := "2.13.12"
+> check213
+> set scalaVersion := "2.12.18"
+> check212

zinc-lm-integration/src/main/scala/sbt/internal/inc/ZincComponentCompiler.scala

@@ -57,7 +57,11 @@ private[sbt] object ZincComponentCompiler {
         scalaInstance: XScalaInstance,
         logger: Logger,
     ): File = lock.synchronized {
-      val raw = new RawCompiler(scalaInstance, ClasspathOptionsUtil.auto, logger)
+      val raw = new RawCompiler(
+        scalaInstance,
+        ClasspathOptionsUtil.autoNoboot(scalaInstance.version),
+        logger
+      )
       val zinc =
         new ZincComponentCompiler(raw, manager, dependencyResolution, bridgeSources, logger)
       logger.debug(f0(s"Getting $bridgeSources for Scala ${scalaInstance.version}"))