rgw_file: split last argv on ws, if provided

This is intended to allow an "extra" unparsed argument string
containing various cmdline options to be passed as the last argument
in the argv array of librgw_create(), which nfs-ganesha is
expecting to happen.

While at it, hook env_args() too.

Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>

src/rgw/librgw.cc

@@ -647,7 +647,18 @@ int librgw_create(librgw_t* rgw, int argc, char **argv)
     std::lock_guard<std::mutex> lg(librgw_mtx);
     if (! g_ceph_context) {
       vector<const char*> args;
+      std::vector<std::string> spl_args;
+      // last non-0 argument will be split and consumed
+      if (argc > 1) {
+	const std::string spl_arg{argv[(--argc)]};
+	get_str_vec(spl_arg, " \t", spl_args);
+      }
       argv_to_vec(argc, const_cast<const char**>(argv), args);
+      // append split args, if any
+      for (const auto& elt : spl_args) {
+	args.push_back(elt.c_str());
+      }
+      env_to_vec(args);
       rc = rgwlib.init(args);
     }
   }