[clang-tools-extra] [clang-doc] fix bug introduced by asset test (PR #97540)

[Petr Hosek via cfe-commits]

petrhosek wrote:

We already have set of CMake variables that we use to refer to `bin` or `lib` directory which account for various configurations: https://github.com/llvm/llvm-project/blob/c02e8f762a410e55581866c43636efcd6504c1bd/llvm/CMakeLists.txt#L446-L467

I think we should introduce another one for the `share` directory and use that.

https://github.com/llvm/llvm-project/pull/97540