knitr does not build vignette
<p>I am writing a package vignette with <code>Rmarkdown</code>. I tried to follow all the tuto from Hadley, Yihui, Rstudio cheat sheet... but I still don't manage to embed the vignette correctly.</p>

<p>For now I have a <code>.Rmd</code> file which compiles fine by pressing Rstudio button "knit". However:</p>

<ul>
<li><code>devtools::build_vignettes()</code> returns <code>NULL</code></li>
<li>building a source package and running <code>R CMD INSTALL</code> does nothing to the <code>/vignettes</code> folder</li>
<li>I have checked the box <code>use roxygen for vignette</code> in Rstudio parameters</li>
<li>when I compile with Rstudio, it saves the .pdf output in a wired temp directory:</li>
</ul>

<blockquote>
  <p>Output created:
  /private/var/folders/53/l9bfpvgj4y7brgnjwym34kph0000gn/T/RtmpydyKqk/preview-ffc141c28b47.dir/mistral-vignette.pdf</p>
</blockquote>

<p>Since my vignette is pretty long to build I would be happy to just include the .pdf output</p>

<hr>

<p>The YAML input:</p>

<pre><code>---
title: "Using mistral for reliability analysis"
author: "Clément Walter"
date: '`r Sys.Date()`'
output: rmarkdown::pdf_document
vignette: &gt;
  %\VignetteIndexEntry{Using mistral for reliability analysis}
  %\VignetteEngine{rmarkdown::render}
  %\VignetteEncoding{UTF-8}
  \usepackage[utf8]{inputenc}
  \DeclareUnicodeCharacter{00A0}{ }
---
</code></pre>

<p>In the DESCRIPTION file, I have added:</p>

<pre><code>VignetteBuilder: knitr
Suggests: knitr, rmarkdown
</code></pre>