`-Z randomize-layout` compiler flag is not documented in the unstable book

[fasterthanlime]

Location

https://doc.rust-lang.org/nightly/unstable-book/compiler-flags.html

Summary

I expected to find a page for -Z randomize-layout, as described in #106764, but I didn't find any.

[ChrisDenton]

A meta note is that we need to do a better job of making sure unstable flags are documented. This isn't the first time this has happened and I suspect there are a number of other unintentionally undocumented flags.

Ideally we'd have CI check for it but I understand that may be more complex than it sounds.