Ensure that context descriptor pointers are signed in the runtime by putting the ptrauth_struct attribute on the types.
We use the new __builtin_ptrauth_struct_key/disc to conditionally apply ptrauth_struct to TrailingObjects based on the signing of the base type, so that pointers to TrailingObjects get signed when used with a context descriptor pointer.
We add new runtime entrypoints that take signed pointers where appropriate, and have the compiler emit calls to the new entrypoints when targeting a sufficiently new OS.
rdar://111480914
We were detaching the child by just modifying the list, but the cancellation path was assuming that that would not be done without holding the task status lock.
This patch just fixes the current runtime; the back-deployment side is complicated.
Fixes rdar://88398824
Take the existing CompatibilityOverride mechanism and generalize it so it can be used in both the runtime and Concurrency libraries. The mechanism is preprocessor-heavy, so this requires some tricks. Use the SWIFT_TARGET_LIBRARY_NAME define to distinguish the libraries, and use a different .def file and mach-o section name accordingly.
We want the global/main executor functions to be a little more flexible. Instead of using the override mechanism, we expose function pointers that can be set by the compatibility library, or by any other code that wants to use a custom implementation.
rdar://73726764
