build: make precompiled headers more useful

This can reduce the compilation time of a release
build (without tests) by more than 40%

Refs: #5212
Change-Id: I977aff0c0c7becbfee8a8b55605b81d0c014829b
diff --git a/tools/nfdc/command-parser.hpp b/tools/nfdc/command-parser.hpp
index e0849b0..52ba292 100644
--- a/tools/nfdc/command-parser.hpp
+++ b/tools/nfdc/command-parser.hpp
@@ -123,6 +123,9 @@
   std::vector<CommandContainer::const_iterator> m_commandOrder;
 };
 
+void
+registerCommands(CommandParser& parser);
+
 } // namespace nfd::tools::nfdc
 
 #endif // NFD_TOOLS_NFDC_COMMAND_PARSER_HPP