Add unit test to demonstrate the 1 cycle saving

Author: Friendseeker

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/A.scala

@@ -0,0 +1,3 @@
+object A {
+  val a: Int = 0
+}

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/B.scala

@@ -0,0 +1,3 @@
+object B {
+  val b = A.a
+}

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/C.scala

@@ -0,0 +1,4 @@
+object C {
+  val c1 = B.b
+  val c2: Int = 0;
+}

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/D.scala

@@ -0,0 +1,3 @@
+object D {
+  val d: Int = C.c2
+}

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/changes/A.scala

@@ -0,0 +1,3 @@
+object A {
+  val a: String = ""
+}

zinc/src/sbt-test/source-dependencies/transitive-early-stopping/test

@@ -0,0 +1,5 @@
+> compile
+
+$ copy-file changes/A.scala A.scala
+> compile
+> checkIterations 4