`nvm install` fails with "Binary download failed, trying source" when
- running on Bash;
- errtrace (`set -E`) is enabled;
- an ERR trap uses `exit` to return a non-zero status; and
- /sbin/init doesn't exist.
Resolved by moving `ls -dl /sbin/init` to the following `if` statement.
In this context, returning non-zero isn't an error and the ERR trap
isn't executed.
Luke Arms