sbt-bridge: Fix lineContent, pointer, pointerSpace
sbt-bridge: Fix lineContent, pointer, pointerSpace

These changes were done to imitate how these fields are set in
https://github.com/sbt/sbt/blob/0.13/compile/interface/src/main/scala/xsbt/DelegatingReporter.scala

The main issue this fixes is sbt displaying the ^ pointer way too far,
because the number of spaces was set from the beginning of the file
instead of the beginning of the line.

lampepfl/dotty,som-snytt/dotty,dotty-staging/dotty,som-snytt/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,som-snytt/dotty,dotty-staging/dotty,som-snytt/dotty