Building on Mac M3: Graphbolt forces OPENMP and CUDA on

## 🐛 Bug

I followed the instructions to build from source at https://docs.dgl.ai/install/index.html#macos and the build failed because it couldn't find OpenMP (which it was searching for even though that is explicitly set to `OFF`). The trace leads to the [graphbolt directory CMakeLists.txt](https://github.com/dmlc/dgl/blob/88f109f17338d7905d6f5618f0b2b3afc689fd54/graphbolt/CMakeLists.txt#L91). `USE_OPENMP` is set to `ON` at this point for some reason (confirmed by sticking a `message` call in there). Throwing `set(OPEN_MP OFF)` immediately above this condition avoids the error, but then there are more errors stemming from graphbolt when building CUDA, even though `USE_CUDA` is `OFF` by default. Setting `-DBUILD_GRAPHBOLT=OFF` gets around these issues, but then the build fails trying to build `tests/cpp/test_spmat_coo.cc` which #includes omp.h. Setting `-DBUILD_CPP_TEST=OFF` got around this issue.

## To Reproduce

Steps to reproduce the behavior:

1. On Mac M3, create a fresh clone of dgl
2. Run commands to build from the documentation:
```shell
mkdir build
cd build
cmake -DUSE_OPENMP=off -DUSE_LIBXSMM=OFF ..
make -j4 # or -j16 or whatever if you have the cores
```

3. Get error about failing to find OpenMP:

```
[ 36%] Built target tensoradapter_pytorch
CMake Error at /Users/gcmn/src/dgl/.venv/lib/python3.12/site-packages/cmake/data/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
Could NOT find OpenMP_C (missing: OpenMP_C_FLAGS OpenMP_C_LIB_NAMES)
Call Stack (most recent call first):
/Users/gcmn/src/dgl/.venv/lib/python3.12/site-packages/cmake/data/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:603 (_FPHSA_FAILURE_MESSAGE)
/Users/gcmn/src/dgl/.venv/lib/python3.12/site-packages/cmake/data/share/cmake-3.30/Modules/FindOpenMP.cmake:600 (find_package_handle_standard_args)
CMakeLists.txt:91 (find_package)

-- Configuring incomplete, errors occurred!
make[2]: *** [CMakeFiles/graphbolt] Error 1
make[1]: *** [CMakeFiles/graphbolt.dir/all] Error 2
```

(aside: it's a bit weird that the stack trace here only lists the path as CMakeLists.txt, rather than graphbolt/CMakeLists.txt. It appears that a separate CMake configure step for graphbolt is getting invoked as part of the build step??).

4. Hack `USE_OPENMP` `OFF`. I originally just put `set(USE_OPENMP OFF)` [right before the if condition](https://github.com/dmlc/dgl/blob/88f109f17338d7905d6f5618f0b2b3afc689fd54/graphbolt/CMakeLists.txt#L90), but it also works to change the [default for the option](https://github.com/dmlc/dgl/blob/88f109f17338d7905d6f5618f0b2b3afc689fd54/graphbolt/CMakeLists.txt#L49). You need to manually delete the separate build directory the graphbolt sub-build created though.

```shell
rm -rf ./* ../graphbolt/build # from build/
cmake -DUSE_OPENMP=off -DUSE_LIBXSMM=OFF ..
make -j16
```

5. Now you get an error about redefinition of `strstr`.

```
In file included from /Users/gcmn/src/dgl/graphbolt/src/cache_policy.cc:20:
In file included from /Users/gcmn/src/dgl/graphbolt/src/./cache_policy.h:28:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/atomic:41:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/__atomic/wait/polling.h:26:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/__atomic/types.h:24:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/__atomic/types/base.h:25:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/__atomic/types/common.h:28:
In file included from /Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/detail/libcxx/include/cstring:72:
/Users/gcmn/src/dgl/graphbolt/../third_party/cccl/libcudacxx/include/cuda/std/detail/libcxx/include/string.h:142:75: error: redefinition of 'strstr'
inline _LIBCUDACXX_INLINE_VISIBILITY _LIBCUDACXX_PREFERRED_OVERLOAD char* strstr(char* __s1, const char* __s2)
^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.4.sdk/usr/include/c++/v1/string.h:104:63: note: previous definition is here
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_PREFERRED_OVERLOAD char* strstr(char* __s1, const char* __s2) {
^
10 errors generated.
make[5]: *** [CMakeFiles/graphbolt_pytorch_2.5.1.dir/src/cache_policy.cc.o] Error 1
make[4]: *** [CMakeFiles/graphbolt_pytorch_2.5.1.dir/all] Error 2
make[3]: *** [all] Error 2
make[2]: *** [CMakeFiles/graphbolt] Error 2
make[1]: *** [CMakeFiles/graphbolt.dir/all] Error 2
```

6. Try again with graphbolt off

```shell
rm -rf ./* ../graphbolt/build # from build/
cmake -DUSE_OPENMP=off -DUSE_LIBXSMM=OFF -DBUILD_GRAPHBOLT=OFF ..
make -j16
```

7. Now you get an error about OpenMP in a test:

```
/Users/gcmn/src/dgl/tests/cpp/test_spmat_coo.cc:4:10: fatal error: 'omp.h' file not found
#include
^~~~~~~
1 error generated.
make[2]: *** [CMakeFiles/runUnitTests.dir/tests/cpp/test_spmat_coo.cc.o] Error 1
```

8. Try again without c++ tests

```shell
rm -rf ./* # from build/
cmake -DUSE_OPENMP=OFF -DUSE_LIBXSMM=OFF -DBUILD_GRAPHBOLT=OFF -DBUILD_CPP_TEST=OFF ..
make -j16
```

9. Success!

## Expected behavior

A build with `USE_OPENMP` and `USE_CUDA` set to `OFF` should not build or look for OpenMP or CUDA and should not build C++ tests that require OpenMP.

## Environment

- DGL Version (e.g., 1.0): HEAD (88f109f17338d7905d6f5618f0b2b3afc689fd54)
- Backend Library & Version (e.g., PyTorch 0.4.1, MXNet/Gluon 1.3): PyTorch 2.5.1 (pip)
- OS (e.g., Linux): macOS Sonoma 14.4
- How you installed DGL (`conda`, `pip`, source): building from source
- Build command you used (if compiling from source): (see above)
- Python version: 3.12.7
- CUDA/cuDNN version (if applicable): N/A
- GPU models and configuration (e.g. V100): Apple M3
- Any other relevant information: N/A