Merge #12668: Doc: do update before fetching packages in WSL build guide

e29c6c8 Ubuntu xenial first dependencies (Nick Vercammen)

Pull request description:

  Add update and upgrade commands to enable the installation of the first dependencies on ubuntu xenial. If those are not executed some packages can not be found.

Tree-SHA512: ad15f8f053703f5b785c307a39b28bd3584fb1f9c32cc166e53955733f03ea3df445959577d65ac8c95c3619a0417894121603f8e656421d30992f4fdd6055f9

Author: laanwj

doc/build-windows.md

@@ -62,6 +62,8 @@ installing the toolchain will be different.
 
 First, install the general dependencies:
 
+    sudo apt update
+    sudo apt upgrade
     sudo apt install build-essential libtool autotools-dev automake pkg-config bsdmainutils curl git
 
 A host toolchain (`build-essential`) is necessary because some dependency