Write intermediate footers in C++

[David Justen]

Hey everyone,

I am currently working on a project using ORC's C++ library. To reduce 
the number of writes, I would like to support multi-partitioned ORC 
files, i.e. multiple valid ORC files in one so that I can read one 
partition through its respective byte range.

I saw that the Writer class from the Java library supports 
`writeIntermediateFooter`, which gives out a byte offset that could be 
used for that purpose. Is there a way to achieve this functionality 
within the C++ library as well?

Best,
David