lint.sh is broken on macOS due to cat -n behavior

[maksimov]

I've been following the contributors' guide and I couldn't get past make lint command as it was giving an error on a vanilla source code. One of the issues is with testing the output of the likes of golint where it is expected to be empty. However echo -n "$OUT" printed out -n instead of nothing, which was then considered as an error condition.

I've tested a substitute command echo "$OUT\c" which does the same thing and works both on macOS and Linux. I will send a PR.

[zimmski]

If you put "Fixes #62" in the commit description of a commit, the issue gets automatically closed if the PR is merged.