The library documentation has references to the one from the backend, so
it should be built after

This commit fixes the following warnings:

  html/GClueClient.html:349: warning: no link for: "gdbus-signal-org-freedesktop-GeoClue2-Client.LocationUpdated" -> ("LocationUpdated").
  html/GClueClient.html:386: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Client.Start" -> (<GTKDOCLINK HREF="Start"><code class="function">Start()</code>).
  html/GClueClient.html:520: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Client.Stop" -> (<GTKDOCLINK HREF="Stop"><code class="function">Stop()</code>).
  html/GClueClient.html:651: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.Location" -> ("Location").
  html/GClueClient.html:744: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.DistanceThreshold" -> ("DistanceThreshold").
  html/GClueClient.html:805: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.DesktopId" -> ("DesktopId").
  html/GClueClient.html:899: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.RequestedAccuracyLevel" -> ("RequestedAccuracyLevel").
  html/GClueClient.html:961: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.Active" -> ("Active").
  html/GClueClient.html:1071: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Client.TimeThreshold" -> ("TimeThreshold").
  html/GClueLocation.html:322: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Latitude" -> ("Latitude").
  html/GClueLocation.html:383: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Longitude" -> ("Longitude").
  html/GClueLocation.html:444: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Accuracy" -> ("Accuracy").
  html/GClueLocation.html:505: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Altitude" -> ("Altitude").
  html/GClueLocation.html:566: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Speed" -> ("Speed").
  html/GClueLocation.html:627: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Heading" -> ("Heading").
  html/GClueLocation.html:688: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Description" -> ("Description").
  html/GClueLocation.html:781: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Location.Timestamp" -> ("Timestamp").
  html/GClueManager.html:266: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Manager.GetClient" -> (<GTKDOCLINK HREF="GetClient"><code class="function">GetClient()</code>).
  html/GClueManager.html:413: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Manager.AddAgent" -> (<GTKDOCLINK HREF="AddAgent"><code class="function">AddAgent()</code>).
  html/GClueManager.html:555: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Manager.InUse" -> ("InUse").
  html/GClueManager.html:617: warning: no link for: "gdbus-property-org-freedesktop-GeoClue2-Manager.AvailableAccuracyLevel" -> ("AvailableAccuracyLevel").
  html/GClueManager.html:755: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Manager.CreateClient" -> (<GTKDOCLINK HREF="CreateClient"><code class="function">CreateClient()</code>).
  html/GClueManager.html:799: warning: no link for: "gdbus-method-org-freedesktop-GeoClue2-Manager.DeleteClient" -> (<GTKDOCLINK HREF="DeleteClient"><code class="function">DeleteClient()</code>).