THRIFT-2474 complete the ntohll precompile conditionals
diff --git a/lib/cpp/src/thrift/protocol/TProtocol.h b/lib/cpp/src/thrift/protocol/TProtocol.h
index f220d5c..f3b6048 100644
--- a/lib/cpp/src/thrift/protocol/TProtocol.h
+++ b/lib/cpp/src/thrift/protocol/TProtocol.h
@@ -97,8 +97,10 @@
 #endif
 
 #if __THRIFT_BYTE_ORDER == __THRIFT_BIG_ENDIAN
+# if !defined(ntohll)
 #  define ntohll(n) (n)
 #  define htonll(n) (n)
+# endif
 # if defined(__GNUC__) && defined(__GLIBC__)
 #  include <byteswap.h>
 #  define htolell(n) bswap_64(n)