[FIXED JENKINS-7926] Add time execution of the build on build detail page

core/src/main/resources/hudson/model/AbstractBuild/index.jelly

@@ -38,6 +38,9 @@ THE SOFTWARE.
         <div style="margin-top:1em">
           ${%startedAgo(it.timestampString)}
           </div><div>
+          <j:if test="${it.building}">
+            ${%beingExecuted(it.executor.timestampString)}
+          </j:if>
           <j:if test="${!it.building}">
             ${%Took} <a href="${rootURL}/${it.parent.url}buildTimeTrend">${it.durationString}</a>
           </j:if>

core/src/main/resources/hudson/model/AbstractBuild/index.properties

@@ -20,4 +20,5 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-startedAgo=Started {0} ago
\ No newline at end of file
+startedAgo=Started {0} ago
+beingExecuted=Build is being executed for {0}
\ No newline at end of file