fix the cert issue (open-cluster-management-io#63)

Signed-off-by: Meng Yan <myan@redhat.com>

Author: yanmxa

federated-learning-controller/deploy/obs/hack/certs/generate-certs.sh

@@ -37,8 +37,16 @@ kubectl --context kind-hub create secret tls otel-signer -n open-cluster-managem
 
 # replace root-ca.crt in deploy/resources/addon-template.yaml
 awk '{print "              " $0}' root-ca.crt > root-ca.crt.tmp
-sed -i "/PROM_WEB_ROOT_CA/{
+# Cross-platform sed in-place editing
+if [[ "$OSTYPE" == "darwin"* ]]; then
+    sed -i '' "/PROM_WEB_ROOT_CA/{
         r root-ca.crt.tmp
         d
     }" ../../otel-addon/resources/addon-template.yaml
+else
+    sed -i "/PROM_WEB_ROOT_CA/{
+        r root-ca.crt.tmp
+        d
+    }" ../../otel-addon/resources/addon-template.yaml
+fi
 rm root-ca.crt.tmp