node to page: Render aliases before pages

Some sites, Hugo docs included, have faulty alias definitions that point
to itself or another real page. These will be overwritten in the next step.

This is how it behaves in Hugo 0.17, too.

Updates #2297

hugolib/site.go

@@ -814,16 +814,20 @@ func (s *Site) render() (err error) {
 	}
 	s.timerStep("prepare pages")
 
-	if err = s.renderPages(); err != nil {
+	// Aliases must be rendered before pages.
-		return
+	// Some sites, Hugo docs included, have faulty alias definitions that point
-	}
+	// to itself or another real page. These will be overwritten in the next
-	s.timerStep("render and write pages")
+	// step.
-
 	if err = s.renderAliases(); err != nil {
 		return
 	}
 	s.timerStep("render and write aliases")
 
+	if err = s.renderPages(); err != nil {
+		return
+	}
+	s.timerStep("render and write pages")
+
 	if err = s.renderSitemap(); err != nil {
 		return
 	}