[LLVMgold] Suppress -Wcast-function-type-mismatch diagnostic

llvm/cmake/modules/HandleLLVMOptions.cmake adds -Wextra.
-Wcast-function-type-mismatch was recently added to -Wextra, leading to
a warning for the `get_wrap_symbols` code (https://reviews.llvm.org/D44235).

Suppress the diagnostic.

Pull Request: https://github.com/llvm/llvm-project/pull/89994