Added xcode-select fix to iOS export page (#8631)

* Added xcode-select fix to iOS export page

---------

Co-authored-by: Max Hilbrunner <mhilbrunner@users.noreply.github.com>

tutorials/export/exporting_for_ios.rst

@@ -128,3 +128,36 @@ the export menu.
      - ``GODOT_IOS_PROVISIONING_PROFILE_UUID_DEBUG``
    * - Options / Application / Provisioning Profile UUID Release
      - ``GODOT_IOS_PROVISIONING_PROFILE_UUID_RELEASE``
+
+Troubleshooting
+---------------
+
+xcode-select points at wrong SDK location
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+xcode-select is a tool that comes with Xcode and among other things points at iOS SDKs on your Mac.
+If you have Xcode installed, opened it, agreed to the license agreement, and installed the command line tools, 
+xcode-select should point at the right location for the iPhone SDK. 
+If it somehow doesn't, Godot will fail exporting to iOS with an error that may look like this:
+
+::
+
+    MSB3073: The command ""clang" <LOTS OF PATHS AND COMMAND LINE ARGUMENTS HERE>
+    "/Library/Developer/CommandLineTools/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk"" exited with code 1.
+
+In this case, Godot is trying to find the ``Platforms`` folder containing the iPhone SDK inside the 
+``/Library/Developer/CommandLineTools/`` folder, but the ``Platforms`` folder with the iPhone SDK is 
+actually located under ``/Applications/Xcode.app/Contents/Developer``. To verify this, you can open 
+up Terminal and run the following command to see what xcode-select points at:
+
+::
+
+    xcode-select -p
+
+To fix xcode-select pointing at a wrong location, enter this command in Terminal:
+
+::
+
+    sudo xcode-select -switch /Applications/Xcode.app
+
+After running this command, Godot should be able to successfully export to iOS.