I was getting this error constantly in eclipse:
Errors during build. Errors running builder \"Integrated External Tool Builder\" on project project. Th
I added this question and answering on my own as I could not find an answer on Stackoverflow and it may benefit someone else
Answer is:
On your project "project", right click -> Properties>Builders Remove the missing builder
Source http://www.eclipse.org/forums/index.php/t/28894/