Prepare for LLVM 18, link to local repo for scripts and patches (#27178)
* Prepare for LLVM 18, link to local repo for scripts and patches
* s/static/shared/
* Change links to upstream repo
* Fix LLVM 18 for OCaml bytecode executables
* Sync hashes with updated patch file
* Set URL to local repo, update hash for llvm.18-static package
* Try building again
* Add zstd depext on freebsd
* Revert "Add zstd depext on freebsd"
This reverts commit c0297d76e481fc6646ab4b9c6145985afa658c93.