The __has_include(<os/system_version.h>) branch here wasn't quite right, we'll just use the dlsym one for now

Author: Catfish-Man

stdlib/public/stubs/Availability.mm

@@ -21,17 +21,6 @@
 #include "swift/Runtime/Debug.h"
 #include <TargetConditionals.h>
 #include "../SwiftShims/FoundationShims.h"
-
-#if __has_include(<os/system_version.h>)
-#include <os/system_version.h>
-
-static os_system_version_s getOSVersion() {
-  struct os_system_version_s vers = { 0, 0, 0 };
-  os_system_version_get_current_version(&vers);
-  return vers;
-}
-
-#else
 #include <dlfcn.h>
 
 struct os_system_version_s {
@@ -50,8 +39,6 @@ static os_system_version_s getOSVersion() {
   return vers;
 }
 
-#endif
-
 using namespace swift;
 
 /// Return the version of the operating system currently running for use in