Bug#1026333: ITP rustup

[matthias.geiger1024@tutanota.de]

Update on the missing deps:

- effective-limits is NEW

- download: needs async-compression (for the reqwest features ) which needs xz2

- xz2: merged. needs lzma-sys (merged)

- zstd: merged. (thanks noctis :) )

- git testament: See https://github.com/kinnison/git-testament/issues/19

Cheers

werdahias