patch to fix old openvdb on new mac os

[alecjacobson]

With a new mac running apple clang 17.0.0, I was getting errors like:

In file included from /Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/util/Util.cc:4:
In file included from /Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/util/Util.h:8:
In file included from /Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/../openvdb/tree/Tree.h:13:
In file included from /Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/../openvdb/tools/Count.h:16:
/Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/../openvdb/tree/NodeManager.h:330:31: error: a template argument list is expected after a name prefixed by the template keyword [-Wmissing-template-arg-list-after-template-kw]
  330 |                 OpT::template eval(mNodeOp, it);
      |                               ^
/Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/../openvdb/tree/NodeManager.h:350:31: error: a template argument list is expected after a name prefixed by the template keyword [-Wmissing-template-arg-list-after-template-kw]
  350 |                 OpT::template eval(mNodeOp, it);
      |                               ^
/Users/ajx/Repos/CoACD/build/_deps/openvdb-src/openvdb/openvdb/../openvdb/tree/NodeManager.h:375:31: error: a template argument list is expected after a name prefixed by the template keyword [-Wmissing-template-arg-list-after-template-kw]
  375 |                 OpT::template eval(*mNodeOp, it);
      |    

It seems like it's related to a problem with modern AppleClang. I tried switching to a modern version of openvdb but that had lots of other issues.

This PR is a pretty gnarly patch of openvdb upon cmake's fetch so that it compiles. Not sure if you want to merge, but at least I put it here for others to find if it's helpful.

[SarahWeiii]

Thank you so much! I will take a look.