Are we able to document the default stack size for threads?

[frewsxcv]

One can specify the stack size of a thread via thread::Builder::stack_size. If one does not use this method when building a thread, it uses some default value, which is specified in util::min_stack.

It looks like util::min_stack looks at the RUST_MIN_STACK env var and attempts to parse it into an integer. If it's not specified or can't parse, it falls back to 2MB.

Should we update the thread documentation to mention what the default stack size is and mention that environment variable?

[frewsxcv]

Relevant discussion on IRC https://botbot.me/mozilla/rust-docs/2017-08-11/?msg=89704992&page=1

[retep998]

Don't forget that the stack size of the main thread is not determined by Rust.

[frewsxcv]

Opened a PR: #43848