Don't warn on unused macros

Change-Id: If12934606c3ef00025d05a9f0b8bd46000865c9a
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/meson.build b/meson.build
index 630fac6..a4315f0 100644
--- a/meson.build
+++ b/meson.build
@@ -161,6 +161,7 @@
     '-Wno-used-but-marked-unused',
     '-Wno-weak-vtables',
     '-Wno-switch-enum',
+    '-Wno-unused-macros',
   ]),
   language:'cpp')
 endif