Cross-build Scala (#17)

* Cross-build Scala

* Adds parenthesis - fixes compilation issue

Author: juanpedromoreno

build.sbt

@@ -1,10 +1,11 @@
 ThisBuild / organization := "org.scala-exercises"
 ThisBuild / githubOrganization := "47degrees"
-ThisBuild / scalaVersion := V.scala
+ThisBuild / scalaVersion := "2.13.3"
+ThisBuild / crossScalaVersions := Seq("2.13.3", "2.12.11")
 
 publish / skip := true
 
-addCommandAlias("ci-test", "scalafmtCheckAll; scalafmtSbtCheck; test")
+addCommandAlias("ci-test", "scalafmtCheckAll; scalafmtSbtCheck; +test")
 addCommandAlias("ci-docs", "github; mdoc; headerCreateAll")
 addCommandAlias("ci-publish", "github; ci-release")
 
@@ -13,7 +14,6 @@ lazy val V = new {
   val circe: String     = "0.13.0"
   val classutil: String = "1.5.1"
   val http4s: String    = "0.21.6"
-  val scala: String     = "2.13.2"
   val scalatest: String = "3.2.0"
 }
 

runtime/src/main/scala/org/scalaexercises/exercises/Exercises.scala

@@ -38,7 +38,8 @@ object Exercises {
       .getURLs
       .map(url => new File(url.getFile)) filter (_.exists)).toSeq
     val classFinder = ClassFinder(files, Some(Opcodes.ASM7))
-    val classes = classFinder.getClasses
+    val classes = classFinder
+      .getClasses()
       .filter(Try(_).isSuccess)
       .toList
     ClassFinder.classInfoMap(classes.iterator)