[CMake] Add backdeployment symbols

Hooks up the definition for back-deployment support and the missing
library name needed to get the magic symbols set up right.

Author: etcwilde

Runtimes/Core/CMakeLists.txt

@@ -87,6 +87,7 @@ defaulted_option(SwiftCore_ENABLE_RUNTIME_OS_VERSIONING "Enable runtime OS versi
 defaulted_option(SwiftCore_ENABLE_STATIC_PRINT "Disable full print")
 defaulted_option(SwiftCore_ENABLE_UNICODE_DATA "Embed Unicode info in Swift Core")
 defaulted_option(SwiftCore_ENABLE_COMPACT_ABSOLUTE_FUNCTION_POINTERS "Resolve absolute function pointer as identity")
+defaulted_option(SwiftCore_ENABLE_BACKDEPLOYMENT_SUPPORT "Add symbols for runtime backdeployment")
 
 defaulted_option(SwiftCore_ENABLE_BACKTRACING "Enable backtracing runtime support")
 defaulted_set(SwiftCore_BACKTRACER_PATH STRING "Set a fixed path to the Swift backtracer")
@@ -113,6 +114,7 @@ add_compile_definitions(
   $<$<BOOL:${SwiftCore_ENABLE_STATIC_PRINT}>:-DSWIFT_STDLIB_STATIC_PRINT> # core + concurrency
   $<$<BOOL:${SwiftCore_ENABLE_UNICODE_DATA}>:-DSWIFT_STDLIB_ENABLE_UNICODE_DATA> # Stubs
   $<$<BOOL:${SwiftCore_ENABLE_ENVIRONMENT}>:-DSWIFT_STDLIB_HAS_ENVIRON> # Concurrency, runtime, shims, platform overlay
+  $<$<BOOL:${SwiftCore_ENABLE_BACKDEPLOYMENT_SUPPORT}>:-DSWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT> # Concurrency, Compatibility override, magic symbols
   $<$<COMPILE_LANGUAGE:C,CXX>:-DSWIFT_RUNTIME_ENABLE_LEAK_CHECKER=$<BOOL:${SwiftCore_ENABLE_RUNTIME_LEAK_CHECKER}>>
   $<$<COMPILE_LANGUAGE:C,CXX>:-DSWIFT_RUNTIME_CLOBBER_FREED_OBJECTS=$<BOOL:${SwiftCore_ENABLE_CLOBBER_FREED_OBJECTS}>>)
 

Runtimes/Core/core/CMakeLists.txt

@@ -300,7 +300,8 @@ target_compile_options(swiftCore PRIVATE
 
 target_compile_definitions(swiftCore PRIVATE
   $<$<BOOL:${SwiftCore_ENABLE_REFLECTION}>:-DSWIFT_ENABLE_REFLECTION>
-  $<$<BOOL:${SwiftCore_ENABLE_COMPACT_ABSOLUTE_FUNCTION_POINTERS}>:-DSWIFT_COMPACT_ABSOLUTE_FUNCTION_POINTER>)
+  $<$<BOOL:${SwiftCore_ENABLE_COMPACT_ABSOLUTE_FUNCTION_POINTERS}>:-DSWIFT_COMPACT_ABSOLUTE_FUNCTION_POINTER>
+  $<$<COMPILE_LANGUAGE:C,CX>:-DSWIFT_TARGET_LIBRARY_NAME=swiftCore>)
 target_compile_options(swiftCore PRIVATE
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xcc -DswiftCore_EXPORTS>")