This is caused by bash thinking that an empty array is the same as an
undefined variable and `set -o nounset` treating that as an error.
Fix that by using an empty string as the default for the expansion.
Fixes PR #1069 (6e25f60288).
Tested:
- Before this patch:
$ mv .git .gitbackup
$ hack/build-go.sh
/home/filbranden/devel/kubernetes/hack/config-go.sh: line 55: ldflags[*]: unbound variable
- After this patch:
$ mv .git .gitbackup
$ rm -rf output/
$ hack/build-go.sh
$ output/go/bin/kubelet -version
Kubernetes version 0.1+, build (unknown)
Signed-off-by: Filipe Brandenburger <filbranden@google.com>