Use a CShim to avoid an unescapable warning about using mktemp

Sources/FoundationEssentials/Data/Data+Writing.swift

@@ -158,7 +158,7 @@ private func createTemporaryFile(at destinationPath: String, inPath: PathOrURL,
 
             // The warning diligently tells us we shouldn't be using mktemp() because blindly opening the returned path opens us up to a TOCTOU race. However, in this case, we're being careful by doing O_CREAT|O_EXCL and repeating, just like the implementation of mkstemp.
             // Furthermore, we can't compatibly switch to mkstemp() until we have the ability to set fchmod correctly, which requires the ability to query the current umask, which we don't have. (22033100)
-            guard mktemp(templateFileSystemRep) != nil else {
+            guard _data_mktemp(templateFileSystemRep) != nil else {
                 throw CocoaError.errorWithFilePath(inPath, errno: errno, reading: false)
             }
 

Sources/_CShims/data_shims.c

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdlib.h>
+#include "data_shims.h"
+
+INTERNAL char *_data_mktemp(char *arg) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated"
+    return mktemp(arg);
+#pragma GCC diagnostic pop
+}

Sources/_CShims/include/data_shims.h

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CSHIMS_DATA_H
+#define CSHIMS_DATA_H
+
+#include "_CShimsMacros.h"
+
+INTERNAL char *_data_mktemp(char *arg);
+
+#endif