fix scala-js

as per Sebastien's advice at scala-js/scala-js#3255

Author: SethTisue

common.conf

@@ -527,6 +527,7 @@ build += {
         //   Although only `testSuite` actually has tests, dbuild will try to run the tests for all projects
         //   that `testSuite` depends on (transitively), so we need to set it in a bunch of places.
         "set Seq(library, testInterface, jUnitRuntime, testSuite).map(p => jsEnv in p := new org.scalajs.jsenv.nodejs.NodeJSEnv(org.scalajs.jsenv.nodejs.NodeJSEnv.Config().withExecutable(\""${vars.node}"\").withSourceMap(false)))"
+        "set MyScalaJSPlugin.wantSourceMaps in testSuite := false"
       ]
     }
   }