Now it got pushed to GitHub. Thanks, @malat.
Issue only exists for GitHub, the ref seems to exist on SF!
So the issue, in short, is that the ref which gets referenced by the submodule (https://github.com/malaterre/gdcmdata/tree/9b38ac7a8baee4e943505ab3c56fb7d19d54754f) isn't there.
3.2.10 updated the Testing/Data submodule, but the new update wasn't pushed to the submodule repo
System::GetHostName unused
https://github.com/malaterre/GDCM/pull/218
There's another section catering legacy CMake just below: #----------------------------------------------------------------------------- +#[[ # Compatibility with older usage of EXECUTABLE_OUTPUT_PATH and LIBRARY_OUTPUT_PATH. # This should be removed in the future. if(EXECUTABLE_OUTPUT_PATH) set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${EXECUTABLE_OUTPUT_PATH}) message(WARNING "EXECUTABLE_OUTPUT_PATH is deprecated. Use CMAKE_RUNTIME_OUTPUT_DIRECTORY instead.") endif() if(LIBRARY_OUTPUT_PATH) set(CMAKE_LIBRARY_OUTPUT_DIRECTORY...
CMake legacy compatibility issue with unconditional setting of -NDEBUG