Build system fixes

[trxcllnt]

• Fix discrepancies in CMake CUDA architecture selection when configure/build are done separately
• Fix ccache's base_dir to point to the repo root so ccache can handle the node-addon-api include paths in <root>/node_modules
• Set PARALLEL_LEVEL=1 as default when building, use dotenv to read .env file for custom env overrides
• Use common build directories for CPM dependencies, so cuDF/cuGraph/cuSpatial bindings don't all end up recompiling cuDF
• Updates branches for libcudf/libcuspatial to take advantage of compile-time optimizations for a smaller libcudf.so

Branched from #128

[bryevdv]

LGTM but merging the other PR left some small conflicts :/