[stdlib] Only emit lexical markers.

Don't use lexical lifetimes fully in the stdlib for now.

Author: nate-chandler

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -1713,6 +1713,7 @@ function(add_swift_target_library name)
   if (SWIFTLIB_IS_STDLIB)
     list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-warn-implicit-overrides")
     list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-Xfrontend;-enable-ossa-modules")
+    list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-Xfrontend;-enable-lexical-lifetimes=false")
   endif()
 
   if(NOT SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER AND NOT BUILD_STANDALONE AND