Allow cuda code to be forcibly generated in non-cuda enviornments such as docker build

Author: clee-ai

setup.py

@@ -1,11 +1,9 @@
 import torch
+import os
 from setuptools import find_packages, setup
 
-has_cuda = torch.cuda.is_available()
-if has_cuda:
- from torch.utils.cpp_extension import BuildExtension, CUDAExtension
-else:
- from torch.utils.cpp_extension import BuildExtension, CppExtension
+from torch.utils.cpp_extension import BuildExtension, CppExtension, CUDAExtension, CUDA_HOME
+has_cuda = (torch.cuda.is_available() and CUDA_HOME is not None) or os.getenv("FORCE_CUDA", "0") == "1"
 
 from torchsparse import __version__