Automatically manage Sourcekite within SDE

[vknabel]

Currently each user has to install sourcekite manually, which takes time and effort. Ideally SDE should automatically download sourcekite and build it against the current Swift version.

Problems:

• Users will change their Swift versions
• The Toolchain does not always have the same location
• There may even exist multiple toolchains (e.g. swiftenv)
• Users will use multiple, incompatible Swift versions (SourceKit 4.0.x was compatible, 4.1 was not and required rebuild)
• It must run reliably on Linux and macOS

Relevant Resources:

• cant build sourcekite for ubuntu 16.04

[vknabel]

A good first step on this would be to create a script that will properly installs sourcekite on all targets.

[vknabel]

Now that sourcekit-lsp has landed in Xcode by default, and we switched to it in 2.10.0 by default, we have a zero-config installation on macOS. 🚀

And as sourcekite is now easier to install, I might even have a another look soon.