Add tests for merge_zips

Test: merge_zip_test.go
Change-Id: I8fc577946b40cad193864aa2ebda1bef3a0e050e
diff --git a/cmd/merge_zips/Android.bp b/cmd/merge_zips/Android.bp
index ace079d..03a5f3b 100644
--- a/cmd/merge_zips/Android.bp
+++ b/cmd/merge_zips/Android.bp
@@ -21,5 +21,8 @@
     srcs: [
         "merge_zips.go",
     ],
+    testSrcs: [
+        "merge_zips_test.go",
+    ],
 }