Merge pull request #5790 from compnerd/IDE-IWYU

Author: swift-ci

include/swift/IDE/CodeCompletionCache.h

@@ -16,6 +16,7 @@
 #include "swift/IDE/CodeCompletion.h"
 #include "swift/Basic/ThreadSafeRefCounted.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include <system_error>
 
 namespace swift {
 namespace ide {