But you are still trying to start with build-tools.jar, not the compiled spigot or bukkit jars.
Could you SSH int othe server, and check what files are placed there? You should see the necesary jar files in that directory.
You could also try to copy the files over again.
You also need both Xmx an Xms filled in, Xms should be about half of what Xmx is.
If selecting the correct jar do not (for some reason) work, you can also edit in the correct jar in server.config in the server driectory. This is really a last resort.