yarn install --immutable [perhaps] should not create yarn.lock from scratch

[dimaqq]

To reproduce:

> cd /
/ > yarn install --immutable
yarn install v1.22.11
info No lockfile found.
[1/4] Resolving packages...
[2/4] Fetching packages...
[3/4] Linking dependencies...
[4/4] Building fresh packages...
success Saved lockfile.
Done in 3.43s.

The documentation for --immutable states that yarn will exit with an error if lock file were to be updated.
Yet in this case, it creates a blank lock file (contents: 2 lines of comments).