Add -sha256 to robolectric zip

This help limit the overhead of cas upload

Change-Id: I4e1dacb38cbebf882457297ddf047a1ad1166504
Test: presubmit
Bug: None
diff --git a/android/test_suites.go b/android/test_suites.go
index b48d71a..63a709f 100644
--- a/android/test_suites.go
+++ b/android/test_suites.go
@@ -68,7 +68,8 @@
 		FlagWithOutput("-o ", outputFile).
 		FlagWithArg("-P ", "host/testcases").
 		FlagWithArg("-C ", testCasesDir.String()).
-		FlagWithRspFileInputList("-r ", outputFile.ReplaceExtension(ctx, "rsp"), installedPaths.Paths())
+		FlagWithRspFileInputList("-r ", outputFile.ReplaceExtension(ctx, "rsp"), installedPaths.Paths()).
+        Flag("-sha256")
 	rule.Build("robolectric_tests_zip", "robolectric-tests.zip")
 
 	return outputFile