$ sbt
> set scala.build.ScriptCommands.enableOptimizer ++ scala.build.ScriptCommands.noDocs ++ ((baseVersionSuffix in Global := "SHA"):: Nil)
[info] Defining */*:baseVersionSuffix, {.}/compile:packageDoc::publishArtifact, {.}/compile:scalacOptions
[info] The new values will be used by */*:versionProperties, bootstrap/*:artifacts and 33 others.
[info] 	Run `last` for details.
[info] Reapplying settings...
[info] *** Welcome to the sbt build definition for Scala! ***
[info] Check README.md for more information.
> publishLocal

...
[info] 	published scala-compiler to /Users/jz/.ivy2/local/org.scala-lang/scala-compiler/2.12.8-bin-4c77697/jars/scala-compiler.jar
[info] 	published ivy to /Users/jz/.ivy2/local/org.scala-lang/scala-compiler/2.12.8-bin-4c77697/ivys/ivy.xml

/code/guardian-frontend on master*
$ git diff head -U2
diff --git a/project/ProjectSettings.scala b/project/ProjectSettings.scala
index f8ffd13797..cf823f4443 100644
--- a/project/ProjectSettings.scala
+++ b/project/ProjectSettings.scala
@@ -26,5 +26,5 @@ object ProjectSettings {
     sources in (Compile,doc) := Seq.empty,
     doc in Compile := target.map(_ / "none").value,
-    scalaVersion := "2.12.7",
+    scalaVersion := "2.12.8-bin-4c77697",
     initialize := {
       val _ = initialize.value
@@ -36,4 +36,6 @@ object ProjectSettings {
       clean.all(allProjects)
     }.value
+  ) ++ Seq(Compile, Test).map(config =>
+    scalacOptions in config := List("-Yprofile-enabled", "-Yprofile-destination", target.value / config.toString + ".csv")
   )

$ sbt -J-Xmx1G clean test:compile clean test:compile
...
Trace file: /Users/jz/code/guardian-frontend/sport/target/test.trace
[info] Done compiling.
Trace file: /Users/jz/code/guardian-frontend/applications/target/test.trace
[info] Done compiling.
[success] Total time: 65 s, completed 05/10/2018 2:19:11 PM

$ (echo '{"traceEvents": [ {"name": "process_name", "ph": "M", "pid": -1, "tid": 2347,"args": {"name": "dummy"}}'; (for f in $(find . -name '*.trace'); do cat $f | perl -pne 's/{"traceEvents": \[\n/,/' |  perl -pne 's/]}//'; done) | egrep -v '^,$'; echo ']}') > /tmp/combined.trace