Xcode 4: Build Failed, No Issues
The first thing I'd try is to clean everything (menu Product / Clean) and the build it again. You might have already tried it.
You'll find (and you can watch during the build) the complete build output in the Log Navigator. That's the right most icon of the small icons just below the Run and Build buttons.
The build (and debug) log files are found in the directory /Users/you/Library/Developer/XCode/DerviedData/YourProject-abcdefg/Logs/Build (and ../Debug respectively).
I don't think there's any output for the installation of your app on the device.