Silence some Mac OS X warnings.
diff --git a/bin/9c b/bin/9c
index 8a7148e..fa37baa 100755
--- a/bin/9c
+++ b/bin/9c
@@ -11,6 +11,7 @@
 		-Wno-parentheses \
 		-Wno-missing-braces \
 		-Wno-switch \
+		-Wno-sign-compare \
 	"
 }