print an error that wraps ExitError

[AkihiroSuda]

Fix #4167

[jandubois]

I think this change is wrong. You should return a non-ExitError if you want limactl to print it. Getting a FATAL error just because a subprocess exited with a non-zero code is annoying. HandleExitError() exists to prevent it from being printed while all other errors still show up.

Now we are getting this:

❯ cat ~/bin/limactl-false
#!/bin/sh
false

❯ limactl false
FATA[0000] external command "/Users/jan/bin/limactl-false" failed  error="exit status 1"

❯ echo $?
1

There should be no output except when the error is internal to limactl itself. Those errors have always been reported (this is from master):

❯ echo false > ~/bin/limactl-nohashbang

❯ chmod +x ~/bin/limactl-nohashbang

❯ limactl-nohashbang

❯ echo $?
1

❯ limactl nohashbang
FATA[0000] external command "/Users/jan/bin/limactl-nohashbang" failed: fork/exec /Users/jan/bin/limactl-nohashbang: exec format error

[jandubois]

Thanks, LGTM