Suppress unused return values when using -c opt.

Change-Id: I9cfe54f1b71d4b2b5e321cd09282db2852664377
diff --git a/third_party/cddlib/BUILD b/third_party/cddlib/BUILD
index 17a7fc4..72ed220 100644
--- a/third_party/cddlib/BUILD
+++ b/third_party/cddlib/BUILD
@@ -26,6 +26,7 @@
     '-Wno-switch-enum',
     '-Wno-empty-body',
     '-Wno-sign-compare',
+    '-Wno-unused-result',
   ] + compiler_select({
       'gcc': ['-Wno-unused-but-set-variable'],
       'clang': []