Update the recommended way of choosing which Xcode to use. (#3081)

* Update the recommended way of choosing which Xcode to use.

We're deprecating the MD_APPLE_SDK_ROOT variable and the setting files.

References:

* dotnet/macios#24021
* dotnet/macios-devtools#140

* Fix typo

* Update docs/macios/includes/choose-xcode-version.md

---------

Co-authored-by: Gerald Versluis <[email protected]>

Author: rolfbjarne

docs/macios/includes/choose-xcode-version.md

@@ -5,18 +5,17 @@ ms.date: 03/19/2024
 
 ## Build with a specific version of Xcode
 
-If you have multiple versions of Xcode installed on your Mac, it's possible to specify which Xcode version should be used when building your app. There are a number of approaches that can be used to accomplish this, but the recommended approach is to set the `MD_APPLE_SDK_ROOT` environment variable to the path of the Xcode version.
+If you have multiple versions of Xcode installed on your Mac, it's possible to specify which Xcode version should be used when building your app. There are a number of approaches that can be used to accomplish this, but there are two recommended approaches:
 
-> [!WARNING]
-> Using `xcode-select -s` to set the version of Xcode to use isn't recommended.
+1. Use `sudo xcode-select --switch ...` to choose the system's currently selected version of Xcode (this requires admin credentials). It's also possible to do this from inside Xcode (Settings -> Locations -> Command Line Tools).
 
-To set the `MD_APPLE_SDK_ROOT` environment variable for the duration of the current terminal session:
+1. Use the `DEVELOPER_DIR` environment variable for the duration of the current terminal session:
 
-1. Open the **Terminal** application.
-1. Type the following command, substituting in your version of Xcode, and press Enter:
+    1. Open the **Terminal** application.
+    1. Type the following command, substituting in your version of Xcode, and press Enter:
 
-    ```zsh
-    export MD_APPLE_SDK_ROOT=/Applications/Xcode_14.1.0.app
-    ```
+        ```zsh
+        export DEVELOPER_DIR=/Applications/Xcode_14.1.0.app
+        ```
 
-If you want to set this environment variable permanently, you can add the `export` command to your shell profile, such as *.zprofile*.
+    If you want to set this environment variable permanently, you can add the `export` command to your shell profile, such as *.zprofile*.

docs/troubleshooting.md

@@ -170,14 +170,15 @@ xcrun: error: unable to find utility "dsymutil", not a developer tool or in PATH
 
 When building an app, .NET for iOS and .NET for Mac Catalyst use the following process to determine which version of Xcode to use:
 
-1. If the `MD_APPLE_SDK_ROOT` environment variable is set, use its value.
-1. If the *~/Library/Preferences/Xamarin/Settings.plist* file exists, use the value defined inside it.
+1. If the `MD_APPLE_SDK_ROOT` environment variable is set, use its value. _This environment variable will be deprecated in a future release; do not use it._
+1. If the *~/Library/Preferences/Xamarin/Settings.plist* or *~/Library/Preferences/maui/Settings.plist* file exists, use the value defined inside it. _These files will be deprecated in a future release; do not use them._
 1. Use the value of `xcode-select -p`.
 1. Use `/Applications/Xcode.app`.
 
-Therefore, the recommended approach to specifying the location of Xcode on your machine is to set the `MD_APPLE_SDK_ROOT` environment variable to the path of the Xcode version. For more information, see [Build with a specific version of Xcode](~/ios/cli.md).
+The recommended approach to specify the location of Xcode on your machine is to:
 
-You can then safely delete *~/Library/Preferences/Xamarin/Settings.plist* from your machine.
+1. Delete *~/Library/Preferences/Xamarin/Settings.plist* or *~/Library/Preferences/maui/Settings.plist* files (if they exist).
+2. Either use `xcode-select --switch ...` to select the system's version of Xcode, or set the `DEVELOPER_DIR` environment variable to the path of Xcode. For more information, see [Build with a specific version of Xcode](~/ios/cli.md).
 
 ## Diagnose issues in Blazor Hybrid apps