[CMake] Export SwiftSyntax targets for inclusion in other build products.

Export all of the SwiftSyntax targets that will be used by other parts of
the toolchain, i.e., the compiler. Clients will import the build
directory's `SwiftSyntaxTargets.cmake` to get targets such as
`SwiftSyntax::SwiftParser` to link against.

Author: DougGregor

CMakeLists.txt

@@ -22,3 +22,8 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(CMAKE_MACOSX_RPATH YES)
 
 add_subdirectory(Sources)
+
+export(EXPORT SwiftSyntaxTargets
+       FILE "${CMAKE_CURRENT_BINARY_DIR}/cmake/SwiftSyntaxTargets.cmake"
+       NAMESPACE SwiftSyntax::
+)

Sources/SwiftDiagnostics/CMakeLists.txt

@@ -22,6 +22,7 @@ set_target_properties(SwiftDiagnostics PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 
 install(TARGETS SwiftDiagnostics
+  EXPORT SwiftSyntaxTargets
   ARCHIVE DESTINATION lib
   LIBRARY DESTINATION lib
   RUNTIME DESTINATION bin)

Sources/SwiftParser/CMakeLists.txt

@@ -42,6 +42,7 @@ set_target_properties(SwiftParser PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 
 install(TARGETS SwiftParser
+  EXPORT SwiftSyntaxTargets
   ARCHIVE DESTINATION lib
   LIBRARY DESTINATION lib
   RUNTIME DESTINATION bin)

Sources/SwiftSyntax/CMakeLists.txt

@@ -62,6 +62,7 @@ set_target_properties(SwiftSyntax PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 
 install(TARGETS SwiftSyntax
+  EXPORT SwiftSyntaxTargets
   ARCHIVE DESTINATION lib
   LIBRARY DESTINATION lib
   RUNTIME DESTINATION bin)