Update dependencies for Enable Fast Compiles (bevyengine#1065)

Added clang as an optional dependency to avoid frustration of running into compile error the first time you run a cargo build

docs/linux_dependencies.md

@@ -9,6 +9,11 @@ If you don't see your distro present in the list, feel free to add the instructi
 ```bash
 sudo apt-get install pkg-config libx11-dev libasound2-dev libudev-dev
 ```
+If you want to Enable Fast Compiles
+```bash
+sudo apt-get install clang
+```
+
 ### Windows Subsystem for Linux (WSL 2)
 
 Graphics and audio need to be configured for them to work with WSL 2 backend.