bitbake: toaster: Hide "Download build log" button if log doesn't exist

Our builds pages show all builds, but also include build requests
which may have resulted in a build failure, before the build
started (e.g. at the recipe parsing stage).

In such cases, the BuildStarted event is not captured by Toaster,
so we have no idea where the log file for the failed build is.

The result is that a build is shown by the Toaster UI /builds/ pages,
but it is really a pretend build which never went beyond being a
build request, and which has no associated log file. In turn, this
breaks the "Download build log" button on the build dashboard,
as there's no log file associated with the build.

Fix this by hiding the "Download build log" button for builds
which don't have a cooker_log_path.

[YOCTO #8373]

(Bitbake rev: 89e6cd03aa11c886f28520557af6c7ad51827b0e)

Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/toastergui/templates/builddashboard.html

@@ -37,7 +37,9 @@
     <span > <i class="icon-warning-sign yellow"></i><strong><a href="#warnings" class="warning show-warnings"> {{build.warnings.count}} warning{{build.warnings.count|pluralize}}</a></strong></span>
 {% endif %}
             <span class="pull-right">Build time: <a href="{% url 'buildtime' build.pk %}">{{ build.timespent_seconds|sectohms }}</a>
-            <a class="btn {%if build.outcome == build.SUCCEEDED%}btn-success{%else%}btn-danger{%endif%} pull-right log" href="{% url 'build_artifact' build.id "cookerlog" build.id %}">Download build log</a>
+            {% if build.cooker_log_path %}
+                <a class="btn {%if build.outcome == build.SUCCEEDED%}btn-success{%else%}btn-danger{%endif%} pull-right log" href="{% url 'build_artifact' build.id "cookerlog" build.id %}">Download build log</a>
+            {% endif %}
             </span>
 
 {%endif%}