Added C++20 CI for OpenVDB and OpenVDB AX

Signed-off-by: Nick Avramoussis <[email protected]>

Author: Idclip

.github/workflows/weekly.yml

@@ -116,6 +116,7 @@ jobs:
           - { name: 'numpy', build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DUSE_NUMPY=ON -DOPENVDB_PYTHON_WRAP_ALL_GRID_TYPES=ON' }
           - { name: 'asan',  build: 'asan',    components: 'core,test,axcore,axtest',          cmake: '-DNANOVDB_USE_OPENVDB=ON -DOPENVDB_AX_STATIC=OFF -DOPENVDB_CORE_STATIC=OFF -DUSE_BLOSC=OFF' } # We never called blosc_destroy(), so disable blosc to silence these errors
           - { name: 'ubsan', build: 'ubsan',   components: 'core,test,axcore,axtest',          cmake: '' }
+          - { name: 'c++20', build: 'Release', components: 'core,test,axcore,axtest',          cmake: '-DCMAKE_CXX_STANDARD=20' }
       fail-fast: false
     steps:
     - uses: actions/checkout@v3