[Windows] Link host tools with 'swiftrt.obj'

swiftrt.obj is required for making things work

Author: rintaro

cmake/modules/AddSwift.cmake

@@ -538,20 +538,26 @@ function(_add_swift_runtime_link_flags target relpath_to_lib_dir bootstrapping)
     set_property(TARGET ${target} APPEND_STRING PROPERTY
                  LINK_FLAGS " -lobjc ")
 
-  elseif(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|ANDROID|OPENBSD|FREEBSD")
+  elseif(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|ANDROID|OPENBSD|FREEBSD|WINDOWS")
     set(swiftrt "swiftImageRegistrationObject${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_OBJECT_FORMAT}-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}")
     if(ASRLF_BOOTSTRAPPING_MODE MATCHES "HOSTTOOLS|CROSSCOMPILE")
       # At build time and run time, link against the swift libraries in the
       # installed host toolchain.
-      get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
-      get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
+      if(SWIFT_PATH_TO_SWIFT_SDK)
+        set(swift_dir "${SWIFT_PATH_TO_SWIFT_SDK}/usr")
+      else()
+        get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
+        get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
+      endif()
       set(host_lib_dir "${swift_dir}/lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
-      set(swiftrt "${host_lib_dir}/${SWIFT_HOST_VARIANT_ARCH}/swiftrt.o")
+      set(host_lib_arch_dir "${host_lib_dir}/${SWIFT_HOST_VARIANT_ARCH}")
 
+      set(swiftrt "${host_lib_arch_dir}/swiftrt${CMAKE_C_OUTPUT_EXTENSION}")
       target_link_libraries(${target} PRIVATE ${swiftrt})
       target_link_libraries(${target} PRIVATE "swiftCore")
 
       target_link_directories(${target} PRIVATE ${host_lib_dir})
+      target_link_directories(${target} PRIVATE ${host_lib_arch_dir})
 
       # At runtime, use swiftCore in the current toolchain.
       # For building stdlib, LD_LIBRARY_PATH will be set to builder's stdlib