Update build library shell script to use 'iphonesimulator'

Update build library shell script to use 'iphonesimulator' instead of 'iphonesimulator7.0' as the sdk has moved forward since Xcode5.1

Just using iphonesimulator should pick-up the default sdk. Works for us on Xcode 5.1 and 5.0.2. This may break compatibility with Xcode 4.