Add oatdump test

Bug: 18000316

Change-Id: Ic22d63dc64a9b7a492b5e6bfbd4c75f30c35dfd5
diff --git a/oatdump/oatdump.cc b/oatdump/oatdump.cc
index 949c2cb..a67ef8f 100644
--- a/oatdump/oatdump.cc
+++ b/oatdump/oatdump.cc
@@ -2302,7 +2302,7 @@
         "  --dump:raw_mapping_table enables dumping of the mapping table.\n"
         "      Example: --dump:raw_mapping_table\n"
         "\n"
-        "  --dump:raw_mapping_table enables dumping of the GC map.\n"
+        "  --dump:raw_gc_map enables dumping of the GC map.\n"
         "      Example: --dump:raw_gc_map\n"
         "\n"
         "  --no-dump:vmap may be used to disable vmap dumping.\n"