buildx failed with: ERROR: failed to solve: process "/bin/sh -c CGO_ENABLED=0 GOOS=linux GOARCH=${GOARCH} go build -a -o gardener-extension-provider-onmetal ./cmd/gardener-extension-provider-onmetal/main.go && CGO_ENABLED=0 GOOS=linux GOARCH=${GOARCH} go build -a -o gardener-extension-admission-onmetal ./cmd/gardener-extension-admission-onmetal/main.go" did not complete successfully: exit code: 1