Revert "Bootstrap with -optimise"

This reverts commit 40e8fc94ef9e0294ac4c18e9766040298029ca03.

Author: OlivierBlanvillain

project/Build.scala

@@ -167,9 +167,6 @@ object Build {
     // otherwise sbt 0.13 incremental compilation breaks (https://github.com/sbt/sbt/issues/3142)
     scalacOptions ++= Seq("-bootclasspath", sys.props("sun.boot.class.path")),
 
-    scalacOptions in Compile += "-optimise",
-    scalacOptions in Test -= "-optimise",
-
     // sbt gets very unhappy if two projects use the same target
     target := baseDirectory.value / ".." / "out" / "bootstrap" / name.value,