Avoid creating a List to initialize fields

[Cherry-picked c3377d4]

Author: lolgab

Diff for: compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -2130,8 +2130,10 @@ class Definitions {
     this.initCtx = ctx
     if (!isInitialized) {
       // force initialization of every symbol that is synthesized or hijacked by the compiler
-      val forced =
-        syntheticCoreClasses ++ syntheticCoreMethods ++ ScalaValueClasses() :+ JavaEnumClass
+      syntheticCoreClasses
+      syntheticCoreMethods
+      JavaEnumClass
+      // end force initialization
       isInitialized = true
     }
     addSyntheticSymbolsComments