When first creating the ARZ file for an archive table, use "wb" as the mode for

gzdopen() because the file itself was only opened for writing (and truncated),
and some libc implementations (like SCO) don't like to do a fdopen(..., "a") on
a fd that was not opened using O_APPEND.

sql/examples/ha_archive.cc

@@ -520,7 +520,7 @@ int ha_archive::create(const char *name, TABLE *table_arg,
     error= my_errno;
     goto error;
   }
-  if ((archive= gzdopen(create_file, "ab")) == NULL)
+  if ((archive= gzdopen(create_file, "wb")) == NULL)
   {
     error= errno;
     goto error2;