Consider recommending building with the Clang plugin

mozilla-central includes an internal Clang plugin that adds static-analysis checks at build-time, to ensure things like proper use of smart pointers in C++: https://firefox-source-docs.mozilla.org/code-quality/static-analysis/existing.html#build-time-static-analysis

A list of checks that are performed by this plugin can be found here: https://searchfox.org/mozilla-central/rev/5a7e5e2e1fe04028fc77787084caf9b26ab74ce6/mfbt/Attributes.h#511

Both comm-central and try-comm-central build with this plugin, so I think we should recommend developers and contributors also enable it for their local builds to prevent bustages, by adding the following to their mozconfig file:

ac_add_options --enable-clang-plugin

A good location for this recommendation could be in this section: https://developer.thunderbird.net/thunderbird-development/building-thunderbird#build-configuration

Open the linked Thunderbird build configuration section and review how local mozconfig options are documented. Add the recommendation to enable the Clang plugin with the provided ac_add_options --enable-clang-plugin snippet, then verify the developer documentation page renders correctly.