prune junit xml files in ci harness

Over time the size of our junit xml has exploded to the point where
test-grid fails to process them. We still have the original/full
*.stdout files from where the junit xml files are generated from so the
junit xml files need NOT have the fill/exact output for
processing/display. So let us prune the large messages with an
indicator that we have "[... clipped...]" some of the content so folks
can see that they have to consult the full *.stdout files.

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

hack/make-rules/test.sh

@@ -240,6 +240,14 @@ produceJUnitXMLReport() {
     rm "${junit_filename_prefix}"*.stdout
   fi
 
+  if ! command -v prune-junit-xml >/dev/null 2>&1; then
+    kube::log::status "prune-junit-xml not found; installing from hack/tools"
+    pushd "${KUBE_ROOT}/cmd/prune-junit-xml" >/dev/null
+      GO111MODULE=on go install .
+    popd >/dev/null
+  fi
+  prune-junit-xml "${junit_xml_filename}"
+
   kube::log::status "Saved JUnit XML test report to ${junit_xml_filename}"
 }