fxc2 does not support option "Fo" which is used by Qt 6's qsb
/Fo Output object file. Often given the extension ".fxc", though other extensions are used, such as ".o", ".obj" or ".dxbc".
Qt 6's qsb uses this option.
Peter Mugaas's efxc2
(https://github.com/JPeterMugaas/efxc2) seems to have support for this. Investigate if switching from fxc2
to efxc2
is feasible.