[UCRT] Import Microsoft.Windows.SDK.CRTSource version 10.0.22621.3

Imported from https://www.nuget.org/packages/Microsoft.Windows.SDK.CRTSource/10.0.22621.3
License: MIT

sdk/lib/ucrt/string/wcsncpy.cpp

@@ -0,0 +1,45 @@
+//
+// wcsncpy.cpp
+//
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+//
+// Defines wcsncpy(), which copies a string from one buffer to another.  This
+// function copies at most 'count' characters.  If fewer than 'count' characters
+// are copied, the rest of the buffer is padded with null characters.
+//
+#include <string.h>
+
+#pragma warning(disable:__WARNING_POSTCONDITION_NULLTERMINATION_VIOLATION) // 26036
+
+
+#ifdef _M_ARM
+    #pragma function(wcsncpy)
+#endif
+
+
+
+extern "C" wchar_t * __cdecl wcsncpy(
+    wchar_t*       const destination,
+    wchar_t const* const source,
+    size_t         const count
+    )
+{
+    size_t remaining = count;
+
+    wchar_t*       destination_it = destination;
+    wchar_t const* source_it      = source;
+    while (remaining != 0 && (*destination_it++ = *source_it++) != 0)
+    {
+        --remaining;
+    }
+
+    if (remaining != 0)
+    {
+        while (--remaining != 0)
+        {
+            *destination_it++ = L'\0';
+        }
+    }
+
+    return destination;
+}