src/gen-lock-obj.sh runs in /bin/sh which does not support echo -n on macOS,
and generates garbage. Resolved by using printf which is posix compliant.

Signed-off-by: Georgi Valkov <gvalkov@abv.bg>

Patch was posted on the mailing list. Awaits inclusion looks like. Fixes
long range build failures on the platform.

Updated Mirror list. The first two seem to not work.

Signed-off-by: Rosen Penev <rosenp@gmail.com>