These also get hidden when linking to the current module privately, so
the forward linking needs bubbled up from these dependencies as well.

The note is "previous definition", not "previous declaration".

Closes #17554

Fixes: #17314

Some third party packages may need to see information only available in
variables defined by the find module. Offer a mechanism to make these
variables available to the caller.

also add generic sdk support

closes #17607

we are still using OpenGL for now

nothing significant in terms of bad code, just minor optimizations

According to upstream, it installs its headers in a subdir, see:
https://github.com/nemtrif/utfcpp/blob/master/CMakeLists.txt#L23

We could also include the subdir in the sources,
but it'd mean not being compatible with previous versions without the subdir:
see https://packages.debian.org/sid/amd64/libutfcpp-dev/filelist

cppcheck warnings in tests are hiding implementation issues.
For now turn of cppcheck issues in the test code so we can
focus on any issues in the VTK implementation code.

Fixes: #17603