scripts: add oe-build-perf-report script

A new tool for pretty-printing build perf test results stored in a Git
repository. The scripts is able to produce either simple plaintext
report showing the difference between two commits, or, an html report
that also displays trendcharts of the test results. The script uses
Jinja2 templates for generating HTML reports so it requires
python3-jinja2 to be installed on the system.

[YOCTO #10931]

(From OE-Core rev: 3b25404f0f99b72f222bdca815929be1cf1cee35)

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/build_perf/html/measurement_chart.html

@@ -0,0 +1,50 @@
+<script type="text/javascript">
+  google.charts.setOnLoadCallback(drawChart_{{ chart_elem_id }});
+  function drawChart_{{ chart_elem_id }}() {
+    var data = new google.visualization.DataTable();
+
+    // Chart options
+    var options = {
+      theme : 'material',
+      legend: 'none',
+      hAxis: { format: '', title: 'Commit number',
+               minValue: {{ chart_opts.haxis.min }},
+               maxValue: {{ chart_opts.haxis.max }} },
+      {% if measurement.type == 'time' %}
+      vAxis: { format: 'h:mm:ss' },
+      {% else %}
+      vAxis: { format: '' },
+      {% endif %}
+      pointSize: 5,
+      chartArea: { left: 80, right: 15 },
+    };
+
+    // Define data columns
+    data.addColumn('number', 'Commit');
+    data.addColumn('{{ measurement.value_type.gv_data_type }}',
+                   '{{ measurement.value_type.quantity }}');
+    // Add data rows
+    data.addRows([
+      {% for sample in measurement.samples %}
+        [{{ sample.commit_num }}, {{ sample.mean.gv_value() }}],
+      {% endfor %}
+    ]);
+
+    // Finally, draw the chart
+    chart_div = document.getElementById('{{ chart_elem_id }}');
+    var chart = new google.visualization.LineChart(chart_div);
+    google.visualization.events.addListener(chart, 'ready', function () {
+      //chart_div = document.getElementById('{{ chart_elem_id }}');
+      //chart_div.innerHTML = '<img src="' + chart.getImageURI() + '">';
+      png_div = document.getElementById('{{ chart_elem_id }}_png');
+      png_div.outerHTML = '<a id="{{ chart_elem_id }}_png" href="' + chart.getImageURI() + '">PNG</a>';
+      console.log("CHART READY: {{ chart_elem_id }}");
+      {% if last_chart == true %}
+        console.log("ALL CHARTS READY");
+      {% endif %}
+      //console.log(chart_div.innerHTML);
+    });
+    chart.draw(data, options);
+}
+</script>
+