Report errors when curl fails

[joshwlewis]

Currently, failures to download the Go distribution from S3 look like this:

    remote: -----> Installing go1.20.8        
    remote: -----> Fetching go1.20.8.linux-amd64.tar.gz...  !     Push rejected, failed to compile Go app.        
    remote: 
    remote:  !     Push failed    

We're using the -s (--silent) flag, so there's no further detail about why the download failed. Adding --show-error to curl will give customers and support agents more context on the reason for the failure.