Exit verify-ios-env immediately on error

If one of the called scripts fails, e.g. because some tooling is missing,
it would still print the "Looks good" message, which is confusing.
Now it just error-exits if one of the called scripts error-exits (which
btw prints an error message and if that's the last thing printed its
more noticable)

libs/verify-ios-environment.sh

@@ -4,6 +4,8 @@
 #
 # This file should be used via `./libs/verify-ios-environment.sh`.
 
+set -e
+
 if [[ ! -f "$(pwd)/libs/build-all.sh" ]]; then
   echo "ERROR: verify-ios-environment.sh should be run from the root directory of the repo"
   exit 1