Fix CUDA_VERSION Comparsion (#165)

cmake/flags.cmake

@@ -91,12 +91,12 @@ foreach(capability 30 35 50)
       list(APPEND __arch_flags " -gencode arch=compute_${capability},code=sm_${capability}")
 endforeach()
 
-if (CUDA_VERSION VERSION_GREATER "7.0")
+if (CUDA_VERSION VERSION_GREATER "7.0" OR CUDA_VERSION VERSION_EQUAL "7.0")
       list(APPEND __arch_flags " -gencode arch=compute_52,code=sm_52")
 endif()
 
 # Modern gpu architectures: Pascal
-if (CUDA_VERSION VERSION_GREATER "8.0")
+if (CUDA_VERSION VERSION_GREATER "8.0" OR CUDA_VERSION VERSION_EQUAL "8.0")
       list(APPEND __arch_flags " -gencode arch=compute_60,code=sm_60")
 endif()