ci : add label for the RISC-V runner (#16150)

.github/workflows/build-riscv-native.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   debian-13-riscv64-native: # Bianbu 2.2
-    runs-on: self-hosted
+    runs-on: [self-hosted, RISCV64]
 
     steps:
       - name: Install prerequisites