feat(setupMac): add xcode install note (tauri-apps#55)

Closes tauri-apps#53.

Author: nothingismagick

docs/getting-started/setup-macos.md

@@ -16,6 +16,11 @@ You will need to have [Homebrew](https://brew.sh/) installed to run the followin
 $ brew install gcc
 ```
 
+You will also need to make sure `xcode` is installed.
+```
+$ xcode-select --install
+```
+
 ### Node Runtime and Package Manager
 
 We recommend using NVM to manage your Node runtime. It allows you to easily switch versions and update Node.
@@ -84,4 +89,4 @@ $ cargo install tauri-bundler --force
 
 ## Continue
 
-Now that you have set up the MacOS-specific dependencies for Tauri, learn how to [add Tauri to your project](/docs/usage/development/integration).
+Now that you have set up the MacOS-specific dependencies for Tauri, learn how to [add Tauri to your project](/docs/usage/development/integration).