Use -enable-ossa-modules for all of stdlib/public (swiftlang#39478)

With this, even non-transparent functions will have their ownership eliminated later in the pipeline

Author: meg-gupta

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -1705,6 +1705,7 @@ function(add_swift_target_library name)
   # behavior for their requirements.
   if (SWIFTLIB_IS_STDLIB)
     list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-warn-implicit-overrides")
+    list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-Xfrontend;-enable-ossa-modules")
   endif()
 
   if(NOT SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER AND NOT BUILD_STANDALONE AND

stdlib/public/core/CMakeLists.txt

@@ -286,7 +286,6 @@ endif()
 
 # STAGING: Temporarily avoids having to write #fileID in Swift.swiftinterface.
 list(APPEND swift_stdlib_compile_flags "-Xfrontend" "-enable-experimental-concise-pound-file")
-list(APPEND swift_stdlib_compile_flags "-Xfrontend" "-enable-ossa-modules")
 
 if(SWIFT_CHECK_ESSENTIAL_STDLIB)
   add_swift_target_library(swift_stdlib_essential ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB IS_STDLIB_CORE