document additional Vanadium build dependencies

static/build.html

@@ -279,6 +279,13 @@
                         <li>python2-protobuf</li>
                     </ul>
 
+                    <p>Additional Vanadium (Chromium) build dependencies not provided by the source tree:</p>
+
+                    <ul>
+                        <li>32-bit glibc</li>
+                        <li>32-bit gcc runtime library</li>
+                    </ul>
+
                     <p>The <code>signify</code> tool (with the proper naming) is also required for signing
                     factory images zips.</p>
                 </section>