...instead of platforms.
Notable changes/flags:
* Append to variables controlling paths and names, to allow for user
configuration
* add `SwiftCore_USE_STATIC_LIBS` to generate static archives
* use PlatformInfo variables to get the platform and arch subfolders
(where appropriate)
* add include guards to ensure PlatformInfo and FindSwiftCore are
included once in a project
* search for the appropriate static or import library under Windows
Addresses rdar://152838903
This matches the case that we use in the Runtimes build system, so we
rely the exported target instead of adding `-lswiftCore`.
Addresses rdar://151700669
This is part of the development component for the module and is part of
the interface definition. This content is consumed by the user during
development.
Extract the `install_swift_interface` function into a new file. This
is always invoked to perform the installation of the Swift interfaces as
well as the binary module. Additionally, it prepares for a future
refactoring which will also install the swift documentation interface.
Adds common CMAKE modules to be used by the supplemental libraries.
Namely:
* ResourceEmbedding
* PlatformInfo
* gyb
* EmitSwiftInterface
* CatalystSupport
