Streamline AndroidMk generation

Add AndroidMkEmitAssignList to emit a line to assign the items from
the given list of string arrays.

Test: treehugger
Change-Id: Id5acbef38ea4e91349bd2461f226db352d4b8123
diff --git a/java/robolectric.go b/java/robolectric.go
index 938abe1..6e8d591 100644
--- a/java/robolectric.go
+++ b/java/robolectric.go
@@ -330,11 +330,10 @@
 	fmt.Fprintln(w, "")
 	fmt.Fprintln(w, "include $(CLEAR_VARS)", " # java.robolectricTest")
 	fmt.Fprintln(w, "LOCAL_MODULE :=", name)
-	fmt.Fprintln(w, "LOCAL_JAVA_LIBRARIES :=", module)
-	fmt.Fprintln(w, "LOCAL_JAVA_LIBRARIES += ", strings.Join(r.libs, " "))
+	android.AndroidMkEmitAssignList(w, "LOCAL_JAVA_LIBRARIES", []string{module}, r.libs)
 	fmt.Fprintln(w, "LOCAL_TEST_PACKAGE :=", String(r.robolectricProperties.Instrumentation_for))
 	fmt.Fprintln(w, "LOCAL_INSTRUMENT_SRCJARS :=", r.roboSrcJar.String())
-	fmt.Fprintln(w, "LOCAL_ROBOTEST_FILES :=", strings.Join(tests, " "))
+	android.AndroidMkEmitAssignList(w, "LOCAL_ROBOTEST_FILES", tests)
 	if t := r.robolectricProperties.Test_options.Timeout; t != nil {
 		fmt.Fprintln(w, "LOCAL_ROBOTEST_TIMEOUT :=", *t)
 	}