Need Help with Gitian-Builder - Missing Signer Error
When you run the gitian-build.sh script, you need to specify additional arguments for it to build and produce gitian signatures. You need to specify the version (or commit or branch) that you want to build. You must also specify an identifier for the GPG key that you want to use to sign the gitian output. That identifier is the signer.

For example, for me, I use the command

./gitian-build.sh -B --kvm 0.16.1 achow101


to build Linux, Windows, and MacOS binaries for 0.16.1 using kvm and signing the gitian output with the key achow101.