main/llvm18: Build with curl to fix debuginfod client support

For debuginfod client functionality in LLVM tooling (like llvm-symbolizer or llvm-debuginfod-find) to actually work, LLVM needs to be build with curl (see 0 and #16972 (closed)). Otherwise, HTTP requests get turned into no-ops, resulting in debuginfod functionality to fail (without any useful error messages). The configuration option is the same across all currently available LLVM versions and we will enable it one by one to not have one single MR with very long build times.

It has been verified that cross-compiliation (via 'bootstrap.sh') still works.