Fix build, add missing comma

Change-Id: I0bb4b63fe6800707873ee77b1365ce2ad177677b
diff --git a/build.gradle b/build.gradle
index 2418fb3..b79c333 100644
--- a/build.gradle
+++ b/build.gradle
@@ -330,7 +330,7 @@
 
 def x20Dependencies = [
     "third_party": [
-        "benchmarks/kotlin-benches"
+        "benchmarks/kotlin-benches",
         "chrome",
         "desugar/desugar_20180308",
         "framework",