opt -dot-callgraph filename on windows

I’m trying to generate a callgraph with clang++ -Iinclude -std=c++17 -S -emit-llvm demo.cpp -o - | opt -analyze -dot-callgraph but I am getting the following error:

Writing ‘.callgraph.dot’… error opening file for writing!

Printing analysis ‘Print call graph to ‘dot’ file’:

Pass::print not implemented for pass: ‘Print call graph to ‘dot’ file’!

I’m using clang 12 on windows. I cannot find a way to supply an alternative filename (-o doesn’t seem to work). Have I missed something in the docs or is this not supported? Either way, this may be enhancement / bug worthy.

Thank you,