[SwiftCore] emit correct names for symbols that can be backdeployed

This matches the flag that was added to the old build system in
b0627e2

Addresses rdar://149410833

Author: edymtt

Runtimes/Core/core/CMakeLists.txt

@@ -301,7 +301,8 @@ target_compile_options(swiftCore PRIVATE
   $<$<COMPILE_LANGUAGE:Swift>:-nostdimport>
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -group-info-path -Xfrontend ${CMAKE_CURRENT_SOURCE_DIR}/GroupInfo.json>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -disable-objc-attr-requires-foundation-module>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -require-explicit-availability=ignore>")
+  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -require-explicit-availability=ignore>"
+  "$<$<AND:$<PLATFORM_ID:Darwin>,$<COMPILE_LANGUAGE:Swift>>:SHELL:-Xfrontend -previous-module-installname-map-file -Xfrontend ${CMAKE_CURRENT_SOURCE_DIR}/PreviousModuleInstallName.json>")
 if(NOT "${CMAKE_BUILD_TYPE}" STREQUAL "MinSizeRel")
   # Using these in MinSizeRel would result in a 15% increase in the binary size
   target_compile_options(swiftCore PRIVATE