Since:
- most are not actually required
- they often don't work with --no-bin-links (the bin scripts called may not exist)
- they cause Yarn to "unplug" the package when using the "Plug and Play" feature
- it's more secure to not run arbitrary code during package installation
Fixes the failures seen in #4418.
Since otherwise it defaults to the tilde version ranges (eg `^1.2.3`),
whereas we choose to use exact version numbers instead. This saves
having to remember to pass `--exact` each time `yarn add` is used.
As of yarn 1.0+ if the version of node or yarn doesn't match that
specified in `package.json`, yarn commands will fail to run and
complain about incompatible versions. Unfortunately the error message
doesn't really make it clear that the user has the wrong version
installed, and instead gives the impression something is broken with
Treeherder. In addition, much of the time the exact version isn't
important, so the user doesn't need to go to the trouble of changing
their node installation.
As such, we just disable the yarn engines check for now.