Fix incOptions in SBT build to avoid spurious recompilations

[retronym]

My first change to our build to turn off SBT's transitive recompilation based on macros has since been neutered by addition of the antOptions setting in scala/scala@f2d0f1e

I think this will fix it:

diff --git a/build.sbt b/build.sbt
index da823d7df7..9c50bef3f4 100644
--- a/build.sbt
+++ b/build.sbt
@@ -337,8 +337,6 @@ lazy val library = configureAsSubproject(project)
         "-doc-root-content", (sourceDirectory in Compile).value + "/rootdoc.txt"
       )
     },
-    // macros in library+reflect are hard-wired to implementations with `FastTrack`.
-    incOptions := incOptions.value.withRecompileOnMacroDef(false),
     includeFilter in unmanagedResources in Compile := "*.tmpl" | "*.xml" | "*.js" | "*.css" | "rootdoc.txt",
     // Include *.txt files in source JAR:
     mappings in Compile in packageSrc ++= {
@@ -366,8 +364,6 @@ lazy val reflect = configureAsSubproject(project)
   .settings(
     name := "scala-reflect",
     description := "Scala Reflection Library",
-    // macros in library+reflect are hard-wired to implementations with `FastTrack`.
-    incOptions := incOptions.value.withRecompileOnMacroDef(false),
     Osgi.bundleName := "Scala Reflect",
     scalacOptions in Compile in doc ++= Seq(
       "-skip-packages", "scala.reflect.macros.internal:scala.reflect.internal:scala.reflect.io"
@@ -881,7 +877,11 @@ lazy val root: Project = (project in file("."))
       }
     },
     antStyle := false,
-    incOptions := incOptions.value.withNameHashing(!antStyle.value).withAntStyle(antStyle.value)
+    incOptions := {
+      val opts = incOptions.value.withNameHashing(!antStyle.value).withAntStyle(antStyle.value)
+      // macros in library+reflect are hard-wired to implementations with `FastTrack`.
+      opts.withRecompileOnMacroDef(false)
+    }
   )
   .aggregate(library, reflect, compiler, interactive, repl, replJline, replJlineEmbedded,
     scaladoc, scalap, partestExtras, junit, libraryAll, scalaDist).settings(

[jvican]

What's the purpose of using Ant style? We wanted to remove it completely in 1.0. Is there any way you can achieve the same behaviour as the patch suggest in an alternative way?