Merge pull request scala#5732 from retronym/topic/build-info-malarkey

More predictable performance of SBT build startup, reload

Author: adriaanm

project/plugins.sbt

@@ -20,3 +20,7 @@ buildInfoKeys := Seq[BuildInfoKey](buildClasspath)
 buildInfoPackage := "scalabuild"
 
 libraryDependencies += "com.typesafe" %% "mima-reporter" % "0.1.13"
+
+concurrentRestrictions in Global := Seq(
+  Tags.limitAll(1) // workaround for https://github.com/sbt/sbt/issues/2970
+)