provide API to use absolute path for SourceInfo

Author: sequencer

core/src/main/scala/chisel3/internal/SourceInfoFileResolver.scala

@@ -16,10 +16,11 @@ private[internal] object SourceInfoFileResolver {
   def resolve(source: scala.reflect.internal.util.SourceFile): String = {
     val userDir = sys.props.get("user.dir") // Figure out what to do if not provided
     val projectRoot = sys.props.get("chisel.project.root")
+    val isAbs = sys.props.get("chisel.project.root.absolute").isDefined
     val root = projectRoot.orElse(userDir)
 
     val path = root.map(r => source.file.canonicalPath.stripPrefix(r)).getOrElse(source.file.name)
     val pathNoStartingSlash = if (path(0) == '/') path.tail else path
-    pathNoStartingSlash
+    if(isAbs) pathNoStartingSlash else source.file.path
   }
 }