init: Simplify struct BuiltinArguments

Make the code that creates BuiltinArguments instances easier to read by
using initializer lists instead of constructor calls. Remove the
BuiltinArguments constructors.

Change-Id: I6cf215a81d298cf7e524e22fb75db820e0225c9a
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/action.cpp b/init/action.cpp
index 1e998ae..18f6360 100644
--- a/init/action.cpp
+++ b/init/action.cpp
@@ -30,7 +30,7 @@
 
 Result<void> RunBuiltinFunction(const BuiltinFunction& function,
                                 const std::vector<std::string>& args, const std::string& context) {
-    auto builtin_arguments = BuiltinArguments(context);
+    BuiltinArguments builtin_arguments{.context = context};
 
     builtin_arguments.args.resize(args.size());
     builtin_arguments.args[0] = args[0];
@@ -69,7 +69,7 @@
 }
 
 Result<void> Command::CheckCommand() const {
-    auto builtin_arguments = BuiltinArguments("host_init_verifier");
+    BuiltinArguments builtin_arguments{.context = "host_init_verifier"};
 
     builtin_arguments.args.resize(args_.size());
     builtin_arguments.args[0] = args_[0];