Comment # 3 on bug 1185203 from Aaron Puchert

(In reply to Christophe Giboudeaux from comment #2)
> libqt5-qttools-doc requires the version that was present at build time.
> 
> So the obvious question is: was it rebuilt?
Problem is that libqt5-qttools-doc is in SLE, and I couldn't convince SUSE to
update the metapackage there. So if you're using the metapackage in SLE you're
going to get llvm7 despite llvm9 and llvm11 being available in SLE. Only Leap
packages default to llvm11.

> As you removed the split libraries in recent llvm versions, I don't think it
> can build successfully in Leap 15.3 unless it gets patched to link to
> clang-cpp.
That might be another problem.

There is a bunch of unfortunate dependencies/conflicts here, and getting rid of
any one of them would solve the issue. Moving the builtin headers from clang7
to libclang7 should be safe and would allow you to drop the clang7 dependency.
I could try to patch the CMake files shipped by LLVM to not be so picky, but
I'm not sure if that works. And lastly I'm not sure whether either of the
unresolvable packages really need libqt5-qttools-doc to build. I don't have it
installed but kdevelop builds fine locally.