Added an implementation of ncclSymGetKernelPtr for when GENERATE_SYM_KERNELS is not defined, as it is normally generated code. (#1925)

src/symmetric.cc

@@ -294,3 +294,9 @@ const char* ncclSymKernelIdToString(int kernelId) {
   }
   return kernelName[kernelId];
 }
+
+#ifndef GENERATE_SYM_KERNELS
+void* ncclSymGetKernelPtr(ncclSymKernelId kernelId, int/*ncclDevRedOp_t*/ red, ncclDataType_t ty) {
+  return nullptr;
+}
+#endif