In clang 21, the -fextend-variable-liveness option was made
default [1] with -Og. It helps reduce "optimized out" problems while
debugging.
However, it conflicts [2] with coroutines.
To prevent problems during the upgrade to Clang 21, disable the option.
[1] 36af7345df
[2] https://github.com/llvm/llvm-project/issues/163007Closesscylladb/scylladb#26573