LLDB changes accessiblity of declarations after type checking,
which is not a good idea because it is likely to break invariants.
Indeed, the validateFixedLayoutAttribute() / hasFixedLayout()
logic was not prepared for this possibility.
This is a targeted fix to address the immediate breakage. A better
fix would be to change LLDB, and also to change Sema to store the
global -enable-resilience flag state in a bit in the serialized
module, instead of sticking it on every declaration.
Fixes <rdar://problem/23545959>.
This is an internal-only affordance for the numerics team to be able to work on SIMD-compatible types. For now, it can only increase alignment of fixed-layout structs and enums; dynamic layout, classes, and other obvious extensions are left to another day when we can design a proper layout control design.
Swift SVN r27323
