[master] abce4bf9d doc: Add detail to the alpine install steps

[Nils Goroll]

commit abce4bf9d96d34111414d7b932d2b2b286872140
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Fri Nov 28 18:27:32 2025 +0100

    doc: Add detail to the alpine install steps

diff --git a/doc/sphinx/installation/install_source.rst b/doc/sphinx/installation/install_source.rst
index f0f09635b..23ca0fcb4 100644
--- a/doc/sphinx/installation/install_source.rst
+++ b/doc/sphinx/installation/install_source.rst
@@ -185,7 +185,9 @@ Build dependencies on Alpine Linux
 
 As of Alpine 3, these steps should install the required dependencies:
 
-* Add the `Alpine Community Repository`_
+* Add the `Alpine Community Repository`_::
+
+        setup-apkrepos -c
 
 * Install dependencies::