Add help guide for SocketException error (#11757)

macOS Sequoia added a new "Local network" permission. Before Flutter
3.29, `flutter run` crashed if the IDE or terminal didn't have this
permission. On Flutter 3.29, `flutter run` provides a helpful error
message that tells the user to turn on Local network permissions.

However, currently >60% of users are on a Flutter SDK before 3.29. This
guide will help these users on an old version of the Flutter SDK resolve
the problem.

Part of: flutter/flutter#150131

## Presubmit checklist

- [x] This PR is marked as draft with an explanation if not meant to
land until a future stable release.
- [x] This PR doesn’t contain automatically generated corrections
(Grammarly or similar).
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Guidelines](https://developers.google.com/style) — for example, it
doesn’t use _i.e._ or _e.g._, and it avoids _I_ and _we_ (first person).
- [x] This PR uses [semantic line
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of 80 characters or fewer.

src/content/get-started/install/help.md

@@ -130,6 +130,35 @@ If you're not using Android Studio,
 you can download the tools using the
 [sdkmanager][] command-line tool.
 
+## macOS setup
+
+### SocketException: Send failed, OS Error: No route to host, errno = 65
+
+__What does this issue look like?__
+
+On macOS, the `flutter run` command produces an error like:
+
+```plaintext
+$ flutter run
+Launching lib/main.dart in debug mode...
+...
+Installing and launching...
+Oops; flutter has exited unexpectedly: "SocketException: Send failed (OS Error: No route to host, errno = 65), address = 0.0.0.0, port = 5353".
+```
+
+__Explanation and suggestions__
+
+This issue is related to macOS permissions.
+
+To fix this:
+
+1. Upgrade your Flutter SDK to the latest version.
+
+2. Open **System Settings** > **Privacy & Security** > **Local Network**.
+   Toggle on the permission for all the code editors and terminals you use to
+   launch Flutter apps.
+   You might need to restart your code editor, terminal, and physical device.
+
 ## Other problems
 
 ### Exit code 69