I'm trying to upload my build to TestFlight.
I've cleaned my project and deleted derived data (which is reccomended).
I've also tried uploading my project via Application Loader, but I also get an error there.
Command/bin/sh failed with exit code 1 error
This isn't really the error. It just indicates that a script was being run using the shell 'sh', and a step within the script failed. You need to find a log or transcript of what it was doing at the time, and look at the error produced by the tool that actually failed.