Swift: fix Windows DLL import library support for CMP0157 NEW

This was accidentally removed when the command templates were
reorganized to introduce the new policy. Restore the flag in the shared
library creation to ensure that we emit the import libraries to the
correct location.

Modules/CMakeSwiftInformation.cmake

@@ -132,7 +132,7 @@ if(CMAKE_Swift_COMPILATION_MODE_DEFAULT)
   endif()
 
   if(NOT CMAKE_Swift_CREATE_SHARED_LIBRARY)
-    set(CMAKE_Swift_CREATE_SHARED_LIBRARY "<CMAKE_Swift_COMPILER> ${CMAKE_Swift_PARALLEL_FLAGS} -emit-library <CMAKE_SHARED_LIBRARY_Swift_FLAGS> <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> <SONAME_FLAG> <TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
+    set(CMAKE_Swift_CREATE_SHARED_LIBRARY "<CMAKE_Swift_COMPILER> ${CMAKE_Swift_PARALLEL_FLAGS} -emit-library <CMAKE_SHARED_LIBRARY_Swift_FLAGS> <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> ${CMAKE_Swift_IMPLIB_LINKER_FLAGS} <SONAME_FLAG> <TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
   endif()
 
   if(NOT CMAKE_Swift_CREATE_SHARED_MODULE)

Tests/RunCMake/Swift/ImportLibraryFlags-check-stdout.txt

@@ -0,0 +1 @@
+.*-implib:lib\\L.lib

Tests/RunCMake/Swift/ImportLibraryFlags.cmake

@@ -0,0 +1,6 @@
+cmake_policy(SET CMP0157 NEW)
+enable_language(Swift)
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+add_library(L SHARED L.swift)

Tests/RunCMake/Swift/RunCMakeTest.cmake

@@ -77,6 +77,14 @@ elseif(RunCMake_GENERATOR STREQUAL Ninja)
       run_cmake_command(ForceResponseFile-check ${CMAKE_COMMAND} --build ${ForceResponseFile_TEST_BINARY_DIR} -- -vn)
     endblock()
 
+    block()
+      if(CMAKE_SYSTEM_NAME MATCHES Windows)
+        set(ImportLibraryFlags_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/SwiftLibraryModuleCommand-build)
+        run_cmake(ImportLibraryFlags)
+        run_cmake_command(ImportLibraryFlags-check ${CMAKE_COMMAND} --build ${SwiftLibraryModuleCommand_TEST_BINARY_DIR} -- -n -v)
+      endif()
+    endblock()
+
     block()
       set(SwiftLibraryModuleCommand_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/SwiftLibraryModuleCommand-build)
       run_cmake(SwiftLibraryModuleCommand)