Increase the maximum heap size on Jenkins

We're getting a lot of OutOfMemoryException when the maximum size is 1
GB, but we cannot increase it too much without using up all the memory
available on the Jenkins instances, let's see if 1.1 GB is enough.

Also stop using a custom -Xss, the default of 1 MB should be good enough.

Author: smarter

project/Build.scala

@@ -6,7 +6,9 @@ import scala.reflect.io.Path
 
 object DottyBuild extends Build {
 
-  val travisMemLimit = List("-Xmx1g", "-Xss2m")
+  // Currently, this cannot be increased without hitting the maximum amount of memory
+  // available on the Jenkins VMs
+  val travisMemLimit = List("-Xmx1100m")
 
   val JENKINS_BUILD = "dotty.jenkins.build"