Fix installation on Windows: add missing DLLs

SwiftPM depends on SwiftDriver and SwiftOptions DLLs, so they should be installed into the toolchain bin directory

Author: egorzhdan

Sources/SwiftDriver/CMakeLists.txt

@@ -88,3 +88,9 @@ set_property(GLOBAL APPEND PROPERTY SWIFTDRIVER_EXPORTS SwiftDriver)
 set_target_properties(SwiftDriver PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 
+if(CMAKE_SYSTEM_NAME STREQUAL Windows)
+  install(TARGETS SwiftDriver
+    ARCHIVE DESTINATION lib
+    LIBRARY DESTINATION lib
+    RUNTIME DESTINATION bin)
+endif()

Sources/SwiftOptions/CMakeLists.txt

@@ -24,3 +24,10 @@ set_property(GLOBAL APPEND PROPERTY SWIFTDRIVER_EXPORTS SwiftOptions)
 # NOTE: workaround for CMake not setting up include flags yet
 set_target_properties(SwiftOptions PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
+
+if(CMAKE_SYSTEM_NAME STREQUAL Windows)
+  install(TARGETS SwiftOptions
+    ARCHIVE DESTINATION lib
+    LIBRARY DESTINATION lib
+    RUNTIME DESTINATION bin)
+endif()