That way, when the request gets truncated by os_log in sourcekit-lsp, we see most of the request. Most likely the sourcetext and the compiler args wouldn't have made it into the log message completely anyway.
rdar://121322828
For example, non-Darwin platforms probably don't want
`#colorLiteral(red:green:blue":alpha:)` and `#imageLiteral(named:)`.
Add an completion option to include them, which is "on" by default.
rdar://75620636