Make std* blocking file-descriptors.

runtime/bin/builtin_natives.cc

Index: runtime/bin/builtin_natives.cc
diff --git a/runtime/bin/builtin_natives.cc b/runtime/bin/builtin_natives.cc
index 5681c0a58b3a08f120aae76f53b3100d1ccda305..c5ef460dcfc7a0862f48acea42b161b81880fff4 100644
--- a/runtime/bin/builtin_natives.cc
+++ b/runtime/bin/builtin_natives.cc
@@ -117,10 +117,11 @@ void FUNCTION_NAME(Logger_PrintString)(Dart_NativeArguments args) {
     // an isolate gets interrupted by the embedder in the middle of
     // Dart_StringToUTF8?  We need to make sure not to swallow the
     // interrupt.
-    Platform::PrintBlocking(stdout, "%s\n", Dart_GetError(result));
+    fprintf(stdout, "%s\n", Dart_GetError(result));
   } else {
-    Platform::PrintBlocking(stdout, "%.*s\n", static_cast<int>(length), chars);
+    fprintf(stdout, "%.*s\n", static_cast<int>(length), chars);
   }
+  fflush(stdout);
 }
 
 }  // namespace bin