CB-7186 --no-signing will be ignored if --buildId is set

Fixed issue:
1. `webworks build --release --buildId 1234 --no-signing`: `--no-signing` was ignored when a `--buildId` is provided
2. `webworks build [--debug] --buildId 1234`: `--buildId` wasn't set in manifest of bar file in debug build
cmdline.js not a command parser for end user, and end user won't see --signing in help message. cmdline.js parses arguments to packager, which inherits ww 1.0 packager.  and --signing is not a real argument to pass to packager, it's just a flag used by package-validate.js.