[llvm] [CMake] Only export the LLVM_LINK_LLVM_DYLIB setting if not yet set (PR #135570)

[Jonas Rembser via llvm-commits]

guitargeek wrote:

> Note that downstream users can choose by specifying `DISABLE_LLVM_LINK_LLVM_DYLIB` in their CMake

Maybe to clarify possible confusion from my previous comment: the `DISABLE_LLVM_LINK_LLVM_DYLIB` argument is not a configuration option for building downstream packages, but a flag that you can set in `llvm_add_library`: https://github.com/llvm/llvm-project/blob/main/llvm/cmake/modules/AddLLVM.cmake#L500

So if you want to build e.g. Clang with disabled dynamic linking, doing `-DDISABLE_LLVM_LINK_LLVM_DYLIB` as you imply would not help because this argument is hardcoded in the `llvm_add_library` calls.


https://github.com/llvm/llvm-project/pull/135570