build.sh: Bump DATE to 20140911

build.sh: Bump DATE to 20140911

This pulls in my proxy-maintained flask-cors [1,2].

[1]: https://bugs.gentoo.org/show_bug.cgi?id=517478
     Summary: dev-python/flask-cors - A Flask extension adding a
       decorator for CORS support
     Ian Delaney (idella4) added my ebuild to the Portage tree [2].
[2]: http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/dev-python/flask-cors/
     Summary: ebuild written by W. T. King, from his overlay
     Date: 2014-09-09 02:56:48Z