fix spconv cuda docker build

Dockerfile

 FROM scrin/dev:latest
 
-RUN cd /root && \
+RUN PROBLEM_FILE=/usr/local/lib/python3.8/dist-packages/torch/share/cmake/Caffe2/Caffe2Targets.cmake && \
+    sed -i 's/-Wall;-Wextra;-Wno-unused-parameter;-Wno-missing-field-initializers;-Wno-write-strings;-Wno-unknown-pragmas;-Wno-missing-braces;-fopenmp//g' $PROBLEM_FILE && \
+    sed -i 's/-Wall;-Wextra;-Wno-unused-parameter;-Wno-missing-field-initializers;-Wno-write-strings;-Wno-unknown-pragmas;-Wno-missing-braces//g' $PROBLEM_FILE && \
+    cd /root && \
     git clone --depth 1 --recursive https://www.github.com/traveller59/spconv.git && \
     cd ./spconv && \
-    python setup.py install
+    SPCONV_FORCE_BUILD_CUDA=1 python setup.py install

setup.py

@@ -15,6 +15,8 @@ from pathlib import Path
 
 LIBTORCH_ROOT = str(Path(torch.__file__).parent)
 
+SPCONV_FORCE_BUILD_CUDA = os.getenv("SPCONV_FORCE_BUILD_CUDA")
+
 PYTHON_VERSION = "{}.{}".format(sys.version_info.major, sys.version_info.minor)
 
 class CMakeExtension(Extension):
@@ -46,7 +48,7 @@ class CMakeBuild(build_ext):
                       '-DPYBIND11_PYTHON_VERSION={}'.format(PYTHON_VERSION),
                       '-DSPCONV_BuildTests=OFF',
                       ] #  -arch=sm_61
-        if not torch.cuda.is_available():
+        if not torch.cuda.is_available() and SPCONV_FORCE_BUILD_CUDA is None:
             cmake_args += ['-DSPCONV_BuildCUDA=OFF']
         else:
             cuda_flags = ["\"--expt-relaxed-constexpr\""]