Remove -Xlink

This mode has not been tested for a while and is not going to be used
in the future. It was the basis on which -from-tasty was created
and tested the loading loading of TASTy trees before -from-tasty existed.

It intended to use the linker call graph to know which classes to reload.
Now that this is not going to be supported this infrastructure is useless.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -52,7 +52,6 @@ class Compiler {
   /** Phases dealing with TASTY tree pickling and unpickling */
   protected def picklerPhases: List[List[Phase]] =
     List(new Pickler) ::            // Generate TASTY info
-    List(new LinkAll) ::            // Reload compilation units from TASTY for library code (if needed)
     List(new ReifyQuotes) ::        // Turn quoted trees into explicit run-time data structures
     Nil
 

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -144,8 +144,6 @@ class ScalaSettings extends Settings.SettingGroup {
   val YshowVarBounds = BooleanSetting("-Yshow-var-bounds", "Print type variables with their bounds")
   val YshowNoInline = BooleanSetting("-Yshow-no-inline", "Show inlined code without the 'inlined from' info")
 
-  /** Linker specific flags */
-  val Xlink = BooleanSetting("-Xlink", "Recompile library code with the application.")
   val YnoDecodeStacktraces = BooleanSetting("-Yno-decode-stacktraces", "Show raw StackOverflow stacktraces, instead of decoding them into triggering operations.")
 
   /** Dottydoc specific settings */

compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala

@@ -390,7 +390,7 @@ class ClassfileLoader(val classfile: AbstractFile) extends SymbolLoader {
   }
 
   private def mayLoadTreesFromTasty(implicit ctx: Context): Boolean =
-    ctx.settings.YretainTrees.value || ctx.settings.Xlink.value || ctx.settings.fromTasty.value
+    ctx.settings.YretainTrees.value || ctx.settings.fromTasty.value
 }
 
 class SourcefileLoader(val srcfile: AbstractFile) extends SymbolLoader {