can't build s390x docker images; skip for now (#265)

cmd/grpcurl/grpcurl.go

@@ -422,7 +422,7 @@ func main() {
 				tlsConf.KeyLogWriter = w
 			}
 
-			creds := credentials.NewTLS(tlsConf)
+			creds = credentials.NewTLS(tlsConf)
 
 			// can use either -servername or -authority; but not both
 			if *serverName != "" && *authority != "" {

releasing/do-release.sh

@@ -47,9 +47,9 @@ echo "$VERSION" > VERSION
 $PREFIX docker run --privileged --rm tonistiigi/binfmt:qemu-v6.1.0 --install all
 # Create a new builder instance
 export DOCKER_CLI_EXPERIMENTAL=enabled
-$PREFIX docker buildx create --use --name multiarch-builder
+$PREFIX docker buildx create --use --name multiarch-builder --node multiarch-builder0
 # push to docker hub, both the given version as a tag and for "latest" tag
-$PREFIX docker buildx build --platform linux/amd64,linux/s390x,linux/arm64 --tag fullstorydev/grpcurl:${VERSION} --tag fullstorydev/grpcurl:latest --push --progress plain --no-cache .
+$PREFIX docker buildx build --platform linux/amd64,linux/arm64 --tag fullstorydev/grpcurl:${VERSION} --tag fullstorydev/grpcurl:latest --push --progress plain --no-cache .
 rm VERSION
 
 # Homebrew release