Starting to work on a full installation story for the Swift runtimes.
This involves generating the SwiftCoreConfig cmake files to allow
importing the just-built runtimes into the overlays and supplemental
libraries, setting up the flags appropriately for the given SwiftCore
build configuration.
This also separates out the development and runtime components to allow
installing just the runtimes without the headers.
Component List:
- SwiftCore_runtime
The runtime libraries that are required for running code.
- SwiftCore_development
The interface with the runtime libraries that are required for
building code against the runtimes.
- SwiftCore_cmake
Files for interfacing CMake projects with the built runtimes.
This includes the target list and flags needed to use the targets
built by the specific configuration used to build the runtime
libraries.
These files are used for mapping flags, definitions, and locations
into the overlay libraries and supplemental libraries.
This adds install commands for the object libraries contributing to
libswiftCore so that they are represented in SwiftCoreTargets.cmake.
Object libraries do not contribute anything to the files actually
installed.
Moving the rest of the references to the compiler source directory to
use the `SwiftCore_SWIFTC_SOURCE_DIR` variable instead of
`${PROJECT_SOURCE_DIR}/../../`.
