tool: correct cast of format argument


Signed-off-by: Xiangfei Ding <xfding@google.com>
Change-Id: I9e6a11b84b9b9372346f653efa822d576a6a6964
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/98407
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

tool/transport_common.cc

diff --git a/tool/transport_common.cc b/tool/transport_common.cc
index 82300a5..8e4c164 100644
--- a/tool/transport_common.cc
+++ b/tool/transport_common.cc
@@ -121,7 +121,8 @@
       reinterpret_cast<char *>(&buffer), 0, nullptr);
   if (len == 0) {
     char buf[256];
-    snprintf(buf, sizeof(buf), "unknown error (0x%x)", error);
+    snprintf(buf, sizeof(buf), "unknown error (0x%x)",
+             static_cast<unsigned>(error));
     return buf;
   }
   std::string ret(buffer, len);