This change introduces a new compilation target platform to the Swift compiler - visionOS.
- Changes to the compiler build infrastrucuture to support building compiler-adjacent artifacts and test suites for the new target.
- Addition of the new platform kind definition.
- Support for the new platform in language constructs such as compile-time availability annotations or runtime OS version queries.
- Utilities to read out Darwin platform SDK info containing platform mapping data.
- Utilities to support re-mapping availability annotations from iOS to visionOS (e.g. 'updateIntroducedPlatformForFallback', 'updateDeprecatedPlatformForFallback', 'updateObsoletedPlatformForFallback').
- Additional tests exercising platform-specific availability handling and availability re-mapping fallback code-path.
- Changes to existing test suite to accomodate the new platform.
If we include this file, it generates inline assembly, which would be fine
except that when apps are being built with bitcode, that isn't allowed.
rdar://103274667
The threading library is being pulled into the compatibility libraries,
but in order to do that we need to make sure it gets built with the
correct deployment target. (Which means we need a special version for
the compatibility libraries.)
rdar://96690200
This is needed in situations where the minimum deployment target is
specified in build-script -- these libraries do not to obey to that
since we need to ensure we are able to back deploy those correctly.
Addresses rdar://59249988
