Fix cuda graph support (#92)

CMakeLists.txt

@@ -82,17 +82,21 @@ FetchContent_MakeAvailable(repo-common repo-core repo-backend)
 #
 if(${TRITON_ENABLE_GPU})
   find_package(CUDAToolkit REQUIRED)
-  message(STATUS "Using CUDA ${CUDA_VERSION}")
+  message(STATUS "Using CUDA ${CUDAToolkit_VERSION}")
   if (WIN32)
     set(CUDA_NVCC_FLAGS -std=c++17)
   else ()
     set(CUDA_NVCC_FLAGS -std=c++11)
   endif ()
 
-  if(CUDA_VERSION VERSION_GREATER "10.1" OR CUDA_VERSION VERSION_EQUAL "10.1")
+  if(NOT DEFINED CUDAToolkit_VERSION)
+    message( FATAL_ERROR "Unable to determine CUDAToolkit_VERSION, CMake will exit." )
+  endif()
+
+  if(CUDAToolkit_VERSION VERSION_GREATER "10.1" OR CUDAToolkit_VERSION VERSION_EQUAL "10.1")
     add_definitions(-DTRITON_ENABLE_CUDA_GRAPH=1)
   else()
-    message(WARNING "CUDA ${CUDA_VERSION} does not support CUDA graphs.")
+    message(WARNING "CUDA ${CUDAToolkit_VERSION} does not support CUDA graphs.")
   endif()
 else()
   message( FATAL_ERROR "TensorRT backend requires TRITON_ENABLE_GPU=1, CMake will exit." )