chore: import upstream snapshot with attribution

Sources/ContainerizationOS/Pipe+Close.swift

@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2025-2026 Apple Inc. and the Containerization project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+extension Pipe {
+    /// Close both sides of the pipe.
+    public func close() throws {
+        var err: Swift.Error?
+        do {
+            try self.fileHandleForReading.close()
+        } catch {
+            err = error
+        }
+        try self.fileHandleForWriting.close()
+        if let err {
+            throw err
+        }
+    }
+
+    /// Ensure that both sides of the pipe are set with O_CLOEXEC.
+    public func setCloexec() throws {
+        if fcntl(self.fileHandleForWriting.fileDescriptor, F_SETFD, FD_CLOEXEC) == -1 {
+            throw POSIXError(.init(rawValue: errno)!)
+        }
+        if fcntl(self.fileHandleForReading.fileDescriptor, F_SETFD, FD_CLOEXEC) == -1 {
+            throw POSIXError(.init(rawValue: errno)!)
+        }
+    }
+}