If _NR_CPUS_value isn't set or empty, prompt about using the current host's threads count.

linux-tkg-config/prepare

@@ -1394,6 +1394,20 @@ CONFIG_DEBUG_INFO_BTF_MODULES=y\r
     fi
   fi
 
+  # NR_CPUS
+  if [ -z "$_NR_CPUS_value" ]; then
+    plain ""
+    plain "Set NR_CPUS value to the current host's threads count?"
+    plain "For best results, it should be equal to the maximum number of threads the target machine has."
+    plain "If you want to use the resulting kernel on a machine with more threads, you can hit enter or answer N to use a default of 128."
+    read -rp "`echo $'    > N/y : '`" CONDITION_nrcpus;
+  fi
+  if [[ "$CONDITION_nrcpus" =~ [yY] ]] || [ -n "$_NR_CPUS_value" ]; then
+    scripts/config --set-val "$_NR_CPUS_value"
+  else
+    scripts/config --set-val "128"
+  fi
+
   fi
 
   # Community patches