Merge pull request swiftlang#23711 from Rostepher/fix-stdlib-install-name-dir

[Build System: CMake] Add back the missing install_name_dir for the standard library.

Author: Rostepher

cmake/modules/AddSwift.cmake

@@ -1029,6 +1029,10 @@ function(_add_swift_library_single target name)
   if(SWIFTLIB_SINGLE_SDK IN_LIST SWIFT_APPLE_PLATFORMS)
     set(install_name_dir "@rpath")
 
+    if(SWIFTLIB_SINGLE_IS_STDLIB)
+      set(install_name_dir "${SWIFT_DARWIN_STDLIB_INSTALL_NAME_DIR}")
+    endif()
+
     # Always use @rpath for XCTest
     if(module_name STREQUAL "XCTest")
       set(install_name_dir "@rpath")