Avoid implicitly dropping const modifier

Summary: Use const_cast instead of implicitly dropping const modifier.

Reviewed By: reanimus

Differential Revision: D6269200

fbshipit-source-id: 61e1708c88a4139d3fdd9cf89f4ff778d0354bb2

folly/ssl/OpenSSLCertUtils.cpp

@@ -199,7 +199,8 @@ std::unique_ptr<IOBuf> OpenSSLCertUtils::derEncode(X509& x509) {
 
 std::vector<X509UniquePtr> OpenSSLCertUtils::readCertsFromBuffer(
     ByteRange range) {
-  BioUniquePtr b(BIO_new_mem_buf(range.data(), range.size()));
+  BioUniquePtr b(
+      BIO_new_mem_buf(const_cast<unsigned char*>(range.data()), range.size()));
   if (!b) {
     throw std::runtime_error("failed to create BIO");
   }