Add notes about XCode also being on the Apple Developer website (#7431)

Josh Taylor and Kirill Bulatov created 

Super minor edit about XCode being on the Apple Developer website, which
can be easier to download and install without needing to go through the
App Store.

Release Notes:
- N/A

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

Change summary

docs/src/developing_zed__building_zed.md | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

Detailed changes

docs/src/developing_zed__building_zed.md 🔗 

@@ -11,7 +11,9 @@ git submodule update --init --recursive
 ## Dependencies
 
 - Install [Rust](https://www.rust-lang.org/tools/install)
-- Install [Xcode](https://apps.apple.com/us/app/xcode/id497799835?mt=12) from the macOS App Store
+- Install [Xcode](https://apps.apple.com/us/app/xcode/id497799835?mt=12) from the macOS App Store, or from the [Apple Developer](https://developer.apple.com/download/all/) website. Note this requires a developer account.
+
+> Ensure you launch XCode after installing, and install the MacOS components, which is the default option.
 
 - Install [Xcode command line tools](https://developer.apple.com/xcode/resources/)
 
@@ -74,7 +76,7 @@ error: failed to run custom build command for gpui v0.1.0 (/Users/path/to/zed)`*
 xcrun: error: unable to find utility "metal", not a developer tool or in PATH
 ```
 
-Try `xcode-select --switch /Applications/Xcode.app/Contents/Developer`
+Try `sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer`
 
 ### Cargo errors claiming that a dependency is using unstable features