Replace DllImport with LibraryImport in SMA 6 (#18581)

src/System.Management.Automation/engine/COM/ComInvoker.cs

@@ -280,7 +280,7 @@ namespace System.Management.Automation
                 {
                     for (int i = 0; i < argCount; i++)
                     {
-                        VariantClear(variantArgArray + s_variantSize * i);
+                        Interop.Windows.VariantClear(variantArgArray + s_variantSize * i);
                     }
 
                     Marshal.FreeCoTaskMem(variantArgArray);
@@ -297,7 +297,7 @@ namespace System.Management.Automation
                 {
                     for (int i = 0; i < refCount; i++)
                     {
-                        VariantClear(tmpVariants + s_variantSize * i);
+                        Interop.Windows.VariantClear(tmpVariants + s_variantSize * i);
                     }
 
                     Marshal.FreeCoTaskMem(tmpVariants);
@@ -305,13 +305,6 @@ namespace System.Management.Automation
             }
         }
 
-        /// <summary>
-        /// Clear variables of type VARIANTARG (or VARIANT) before the memory containing the VARIANTARG is freed.
-        /// </summary>
-        /// <param name="pVariant"></param>
-        [DllImport("oleaut32.dll")]
-        internal static extern void VariantClear(IntPtr pVariant);
-
         /// <summary>
         /// We have to declare 'bstrSource', 'bstrDescription' and 'bstrHelpFile' as pointers because
         /// CLR marshalling layer would try to free those BSTRs by default and that is not correct.

src/System.Management.Automation/engine/ComInterop/InteropServices/Variant.cs

@@ -276,9 +276,6 @@ namespace System.Management.Automation.InteropServices
             }
         }
 
-        [DllImport("oleaut32.dll")]
-        internal static extern void VariantClear(IntPtr variant);
-
         /// <summary>
         /// Release any unmanaged memory associated with the Variant
         /// </summary>
@@ -306,7 +303,7 @@ namespace System.Management.Automation.InteropServices
                 {
                     fixed (void* pThis = &this)
                     {
-                        VariantClear((IntPtr)pThis);
+                        Interop.Windows.VariantClear((nint)pThis);
                     }
                 }
 

src/System.Management.Automation/engine/Interop/Windows/VariantClear.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#nullable enable
+
+#if !UNIX
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Windows
+    {
+        [LibraryImport("oleaut32.dll")]
+        internal static partial void VariantClear(nint pVariant);
+    }
+}
+#endif