Remind user about missing system packages

When installing a Linux toolchain without a post-install file there's a brief message about the system packages that are needed for the toolchain. What happens if a user forgets about the message, logs out of ssh, or clears their terminal? The only opportunity to discover what those packages were is by installing (or uninstalling/reinstalling) a toolchain again, which is time consuming.

There should be a mechanism for the user to pull up the missing packages for a toolchain after the initial installation without having to work around it. Ideally, there will be a warning if they try to use or proxy to a toolchain that doesn't have all of its dependencies met. That could be another opportunity to present the user with the actionable message.

Start by tracing where installation emits the brief system-package message and where users invoke or proxy to a toolchain. Define how missing packages can be retrieved after installation and when a dependency warning should appear. Done means users have a reliable way to rediscover the actionable package message without reinstalling a toolchain.