Hi,
I am facing the same problem, fixing the gdcm package in the Debian.
gdcm worked fine with VTK_9.1, but does not work with 9.3.
As pointed earlier CMAKE_INSTALL_DATAROOTDIR is really empty. Should it be fixed in VTK?
Bug description: #1072822 - gdcm FTBFS with VTK 9.3.0 - Debian Bug report logs
Logs: Build log for gdcm (3.0.24-1+b2) on amd64
It would be nice to get a response to fix the build.
Thank you