Add missing onSourceCompiled callback

Author: WojciechMazur

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -4,6 +4,7 @@ import dotty.tools.dotc.CompilationUnit
 import dotty.tools.dotc.core.Phases.Phase
 import dotty.tools.dotc.report
 import dotty.tools.dotc.core._
+import dotty.tools.dotc.interfaces.CompilerCallback
 import Contexts._
 import Symbols._
 import dotty.tools.io._
@@ -70,6 +71,10 @@ class GenBCode extends Phase { self =>
     // In Scala 3 we don't perform backend optimizations and though always post process without the delay
     // https://github.com/scala/scala/pull/6057
     postProcessor.postProcessAndSendToDisk(generated)
+    (ctx.compilerCallback: CompilerCallback | Null) match {
+      case cb: CompilerCallback => cb.onSourceCompiled(ctx.source)
+      case null => ()
+    }
 
   override def runOn(units: List[CompilationUnit])(using ctx:Context): List[CompilationUnit] = {
     try super.runOn(units)