Decrease maximum heap size

The Jenkins VMs do not have enough memory to let us use a heap of 1.5G,
let's see if a heap of 1.25G is enough to avoid OutOfMemoryExceptions.

Author: smarter

project/Build.scala

@@ -8,8 +8,7 @@ object DottyBuild extends Build {
 
   val JENKINS_BUILD = "dotty.jenkins.build"
 
-  // This is what sbt uses (http://www.scala-sbt.org/0.13/docs/Manual-Installation.html)
-  val memoryOptions = List("-Xms512M", "-Xmx1536M", "-Xss1M")
+  val memoryOptions = List("-Xms512M", "-Xmx1250M", "-Xss1M")
 
   val agentOptions = List(
     // "-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005"