Build threading library

Author: etcwilde

Runtimes/Core/CMakeLists.txt

@@ -25,3 +25,4 @@ include_directories(include)
 add_subdirectory(LLVMSupport)
 add_subdirectory(SwiftShims/swift/shims)
 add_subdirectory(Demangling)
+add_subdirectory(Threading)

Runtimes/Core/Threading/CMakeLists.txt

@@ -0,0 +1,10 @@
+# TODO: I think we can build the one that actually matters based on the
+#       platform we're building, rather than relying just on macro definitions
+#       and linking empty objects.
+#       https://github.com/swiftlang/swift/issues/77435
+add_library(swiftThreading OBJECT
+  "${PROJECT_SOURCE_DIR}/../../lib/Threading/C11.cpp"
+  "${PROJECT_SOURCE_DIR}/../../lib/Threading/Linux.cpp"
+  "${PROJECT_SOURCE_DIR}/../../lib/Threading/Pthreads.cpp"
+  "${PROJECT_SOURCE_DIR}/../../lib/Threading/Win32.cpp")
+target_link_libraries(swiftThreading PRIVATE swiftShims)