Fix trivial warnings hidden by -isystem

Fix the trivial warnings that are hidden by the use of -isystem to
include frameworks/av and caught by -Werror.

Test: m -j checkbuild
Bug: 31751828
Change-Id: I155f9f772ce0a84b364313814cb7cf528b9de4eb
diff --git a/media/libnbaio/include/NBLog.h b/media/libnbaio/include/NBLog.h
index 68c31af..19232ff 100644
--- a/media/libnbaio/include/NBLog.h
+++ b/media/libnbaio/include/NBLog.h
@@ -469,7 +469,7 @@
                                          String8 *timestamp,
                                          String8 *body);
     // dummy method for handling absent author entry
-    virtual void handleAuthor(const AbstractEntry &fmtEntry, String8 *body) {}
+    virtual void handleAuthor(const AbstractEntry& /*fmtEntry*/, String8* /*body*/) {}
 
     static void drawHistogram(String8 *body, const std::vector<int64_t> &samples,
                               bool logScale, int indent = 0, int maxHeight = 10);