hotfix: patch error handling (#1293)

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## 📌 Description

import failure without cudnn

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Author: aleozlx

flashinfer/gemm.py

@@ -25,13 +25,19 @@
 import torch
 import torch.nn.functional as F
 
+CUDNN_AVAILABLE = False
 try:
     import cudnn
 
     CUDNN_AVAILABLE = True
 except ImportError:
-    cudnn = None
-    CUDNN_AVAILABLE = False
+    pass
+except OSError as e:
+    error_msg = str(e).lower()
+    is_lib_missing = any(ext in error_msg for ext in [".so", ".dll"])
+    if not is_lib_missing:
+        raise
+
 
 from .jit import JitSpec
 from .jit import env as jit_env