tools: Use binary mode for output writing in ndngetfile

Change-Id: I1c7954517b65e81b1e0ab9d336a6c69d76390d17
Refs: #2296
diff --git a/tools/ndngetfile.cpp b/tools/ndngetfile.cpp
index db1b22b..99f54ca 100644
--- a/tools/ndngetfile.cpp
+++ b/tools/ndngetfile.cpp
@@ -290,12 +290,11 @@
 
   if (outputFile != 0)
     {
-      of.open(outputFile);
-      if (!of)
-        {
-          std::cerr << "ERROR: output file is invalid" << std::endl;
-          return 1;
-        }
+      of.open(outputFile, std::ios::out | std::ios::binary | std::ios::trunc);
+      if (!of || !of.is_open()) {
+        std::cerr << "ERROR: cannot open " << outputFile << std::endl;
+        return 1;
+      }
       buf = of.rdbuf();
     }
   else