ci: show distribution information

The lsb-release command is missing on our images; just show the
information from the file instead of relying on it.

azure-pipelines/build.sh

@@ -26,7 +26,7 @@ fi
 
 if [ -f "/etc/debian_version" ]; then
 	echo "Debian version:"
-	lsb_release -a | indent
+	(source /etc/lsb-release && echo "${DISTRIB_DESCRIPTION}") | indent
 fi
 
 echo "Kernel version:"