am 89919a03: Merge "Include bn.h for BN_ functions."

* commit '89919a03f0eee8f9413c0ed64ef0e7fd5388557b':
  Include bn.h for BN_ functions.
diff --git a/verity/build_verity_tree.cpp b/verity/build_verity_tree.cpp
index 1c3815d..1281c6a 100644
--- a/verity/build_verity_tree.cpp
+++ b/verity/build_verity_tree.cpp
@@ -1,3 +1,4 @@
+#include <openssl/bn.h>
 #include <openssl/evp.h>
 #include <sparse/sparse.h>