now that distros are starting to adopt gcc-14, it's time to revisit our supported compiler versions ceph has been pinned to gcc-11 ever since we enabled c++20 in https://github.com/ceph/ceph/pull/45133 this means that we're now trying to support 4 gcc major versions. an example where this is problematic: gcc-14 complains about the use of deprecated overloads atomic_store_explicit/atomic_load_explicit in ceph_context.h, with a warning that says "use 'std::atomic<std::shared_ptr<T>>' instead". i made this change in https://github.com/ceph/ceph/pull/58176, but it fails to compile under gcc-11 with "std::atomic requires a trivially copyable type". that works fine in gcc-12 and later crimson builds recently switched to gcc-13 in https://github.com/ceph/ceph/pull/55886, but an lto-related bug in gcc prevented the whole project from switching. in order to make that switch, we'll either need to: a) verify that the compiler bug is resolved in all supported distros, or b) measure the performance impact of disabling lto and decide whether it's significant if we're not able to switch to gcc-13 yet, then we should require at least gcc-12