Tweak the way compile dependencies for junit configurations are exported

Change-Id: Ib20e9a3ca1606747412e9eb30c5d28142835064f
diff --git a/build.gradle b/build.gradle
index 6dfb890..6e0a62e 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,8 +1,9 @@
 apply plugin: 'java'
 
 configurations {
-    host
-    target
+    // similar to 'default', export compile-time dependencies
+    host.extendsFrom(hostCompile)
+    target.extendsFrom(targetCompile)
 }
 
 sourceSets {
@@ -32,7 +33,7 @@
 dependencies {
     targetCompile getAndroidPrebuilt('4')
     targetCompile project(':hamcrest')
-    
+
     hostCompile project(':hamcrest')
 }