[misc] improve error message for "Failed to infer device type" (#15994)

Signed-off-by: youkaichao <youkaichao@gmail.com>

vllm/config.py

@@ -1875,7 +1875,10 @@ class DeviceConfig:
             from vllm.platforms import current_platform
             self.device_type = current_platform.device_type
             if not self.device_type:
-                raise RuntimeError("Failed to infer device type")
+                raise RuntimeError(
+                    "Failed to infer device type, please set "
+                    "the environment variable `VLLM_LOGGING_LEVEL=DEBUG` "
+                    "to turn on verbose logging to help debug the issue.")
         else:
             # Device type is assigned explicitly
             self.device_type = device