[Makefile] fix compilation error on macOS
`make` will result into below below error without fix on macOS
```
cp -f bin/hyperfed-linux images/federation-v2/hyperfed
cp: bin/hyperfed-linux: No such file or directory
make: *** [container] Error 1
```
@@ -76,7 +76,7 @@ vet:
fmt:
$(shell ./hack/update-gofmt.sh)
-container: hyperfed
+container: $(HYPERFED_TARGET)-linux
cp -f $(HYPERFED_TARGET)-linux images/federation-v2/hyperfed
$(DOCKER) build images/federation-v2 -t $(IMAGE_NAME)
rm -f images/federation-v2/hyperfed
