Fix build with Clang on FreeBSD
diff --git a/lens_default.c b/lens_default.c
index ed3d0e1..9f60dae 100644
--- a/lens_default.c
+++ b/lens_default.c
@@ -673,7 +673,7 @@
 	unsigned neg = bits > sz * 4 ? 0xff : 0x00;
 
 	int o = 0;
-	if (acc_fprintf(&o, stream, "%s<", "~" + (neg == 0x00)) < 0)
+	if (acc_fprintf(&o, stream, "%s<", &"~"[neg == 0x00]) < 0)
 		return -1;
 
 	size_t bitno = 0;