[arch-dev-public] Caution when moving packages built against glibc 2.27

Care should be taken when building against glibc 2.27 (which is currently in [staging]). In particular: - While glibc 2.27 is in [staging], new rebuilds should not be started. - After glibc 2.27 migrates to [testing], packages built against it should remain in [testing] until glibc 2.27 lands in [core]. The above considerations must be taken into account because packages built against glibc 2.27 might depend on versioned symbols that are not found in glibc 2.26 and thus will not work. [1] [1] https://bugs.archlinux.org/task/58216