cmd/coordinator: add link to known issue on builders page

The tooltip for builders with a known issue is displayed consistently
as of the last commit, but accessing a link in a tooltip is not easy.
It's reasonable to expect that known issues would be linked on the
builders page. Add a column with links there to make it so.

For golang/go#42405.

Change-Id: I5e915132f2ca05efc69bc76da1f25b897569be5d
Reviewed-on: https://go-review.googlesource.com/c/build/+/370335
Trust: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: dmitshur

cmd/coordinator/builders.go

@@ -92,13 +92,14 @@ var buildersTmpl = template.Must(template.New("builders").Funcs(template.FuncMap
 <h2 id='builders'>Defined Builders</h2>
 
 <table>
-<thead><tr><th>name</th><th>pool</th><th>owners</th><th>notes</th></tr>
+<thead><tr><th>name</th><th>pool</th><th>owners</th><th>known issue</th><th>notes</th></tr>
 </thead>
 {{range .Builders}}
 <tr>
 	<td>{{.Name}}</td>
 	<td><a href='#{{.HostType}}'>{{.HostType}}</a></td>
 	<td>{{builderOwners .}}</td>
+	<td>{{with .KnownIssue}}<a href="https://go.dev/issue/{{.}}" title="This builder has a known issue. See go.dev/issue/{{.}}.">#{{.}}</a>{{end}}</td>
 	<td>{{.Notes}}</td>
 </tr>
 {{end}}