Skip sourceroot and targetroot for in JavaTarget when semanticDbEnabl…

…edAlternatively

Mill handles semanticdb differently and the Scala compilation is
already skipping these checks. Two checks were missing though,
for Java compilation

metals/src/main/scala/scala/meta/internal/metals/JavaTarget.scala

@@ -33,9 +33,11 @@ case class JavaTarget(
   def isSemanticdbEnabled: Boolean =
     javac.isSemanticdbEnabled || semanticDbEnabledAlternatively
 
-  def isSourcerootDeclared: Boolean = javac.isSourcerootDeclared
+  def isSourcerootDeclared: Boolean =
+    javac.isSourcerootDeclared || semanticDbEnabledAlternatively
 
-  def isTargetrootDeclared: Boolean = javac.isTargetrootDeclared
+  def isTargetrootDeclared: Boolean =
+    javac.isTargetrootDeclared || semanticDbEnabledAlternatively
 
   def classDirectory: String = javac.getClassDirectory()