First hack pass at cross-build discovery and command-running now works.

Can be tested out on our `build.sc` via `scalaplugin/target/mill run Core.cross[a].printIt`

Needs tons of cleanup...

1 files changed, 6 insertions, 0 deletions

diff --git a/build.sc b/build.sc
index 821780b6..ca57bb99 100755
--- a/build.sc
+++ b/build.sc
@@ -20,6 +20,12 @@ object Core extends ScalaModule {
 
   def basePath = pwd / 'core
   override def sources = pwd/'core/'src/'main/'scala
+
+  val cross = for(c <- mill.define.Cross("a", "b", "c")) yield new mill.Module{
+    def printIt() = T.command{
+      println("PRINTING IT: " + c)
+    }
+  }
 }
 object CoreTests extends ScalaModule {
   def scalaVersion = "2.12.4"