Add WSL2 workaround to 'Get Frama-C' page

html/get-frama-c.html

@@ -61,8 +61,7 @@ opam install frama-c
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 					<pre class="shell-win">
 <span class="shell-win-comment"># 1. Prepare opam installation</span>
-sudo apt update
-sudo apt upgrade
+sudo apt update &amp;&amp; sudo apt upgrade
 sudo apt install make m4 gcc opam
 
 <span class="shell-win-comment"># 2. opam setup</span>
@@ -76,6 +75,8 @@ opam depext --install -y lablgtk3 lablgtk3-sourceview3
 <span class="shell-win-comment"># 4. Install Frama-C</span>
 opam depext --install -y frama-c
 
+<span class="shell-win-comment"># On WSL2, run the GUI as: </span>GDK_BACKEND=x11 frama-c-gui &lt;options&gt;
+
 <span class="shell-win-comment"># Issues? Problems? <a target="_blank" class="shell-link shell-win" href="https://git.frama-c.com/pub/frama-c/blob/master/INSTALL.md">Click here for help/instructions</a></span></pre>
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