Add build note for Nim 2.0.0

[woolsweater]

When building with v2 of the language repo, nimsuggest wants to import sha1 from under the 'dist/' directory: https://github.com/nim-lang/Nim/blob/v2.0.0/nimsuggest/nimsuggest.nim#L19 That directory is generated in the course of building the main Nim repository; without it nimsuggest will not build and therefore building nimlsp will also fail.

[PMunch]

Hmm, what a strange bug.. We should look into which part of build_all actually does this step so that we can potentially do it ourselves.

[Karrq]

I just incurred in this issue when building nimble via nix for nim2 (since the nix package doesn't build nimble from nim sources).
I also noticed dist wasn't part of the installed package, and I found that niminst doesn't add the dist folder to the list of folders to copy over in the final install.sh, probably because it's just in the "[Other]" section of installer.ini