Add a note about using LLD

Author: Kobzol

docs/development.md

@@ -68,6 +68,16 @@ Everytime you want to run bors:
   - Configure the webhook URL for your app to point to `<address>/github`.
 - Try `@bors ping` on some PR on the test repository :)
 
+## Faster compilation
+Bors has a lot of dependencies and can be fairly slow to compile. If you want to improve compilation speed, you could use a faster linker, e.g. LLD.
+
+To do that, install it (e.g. using `sudo apt install lld`) and then put this:
+```toml
+[build]
+rustflags = ["-C", "link-arg=-fuse-ld=lld"]
+```
+into `.cargo/config.toml`.
+
 ## Database
 You must have `sqlx-cli` installed for the following commands to work.
 ```console