title: Make UIStackView hug its content
body: <p>I'm trying to implement a basic layout using a main horizontal <code>UIStackView</code>, with 2 children vertical <code>UIStackViews</code>.</p>
  <p><a href="https://i.stack.imgur.com/8abk2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8abk2.png" alt="enter image description here" /></a></p>
  <p>Here is what I want:</p>
  <ul>
  <li>the red view has 2 constraints: width = height = 50</li>
  <li>the left vertical stackview(with the green label) should be as wide as its largest child, and should center all children horizontally.</li>
  <li>the right vertical stackview(with the yellow label) should take up all available space.</li>
  </ul>
  <p>Setting the alignment of the left vertical stack to <code>fill</code> expands the yellow label but do makes the red and green views have the same width. Changing the alignment to <code>center</code> make the left stack not hug it's children (just like in the image).</p>
  <p><a href="https://i.stack.imgur.com/Ozhy8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ozhy8.png" alt="enter image description here" /></a></p>
  <p>Any ideas how this should be done?</p>