Update build script.

Build/build.ps1

@@ -39,11 +39,11 @@ if ($path) {
 
 	Remove-Item .\NuGet -Force -Recurse -ErrorAction SilentlyContinue
 
-    Copy-Item MQTTnet.AspNetCore.nuspec -Destination MQTTnet.AspNetCore.nuspec.old
+    Copy-Item MQTTnet.AspNetCore.nuspec -Destination MQTTnet.AspNetCore.nuspec.old -Force
 	(Get-Content MQTTnet.AspNetCore.nuspec) -replace '\$nugetVersion', $nugetVersion | Set-Content MQTTnet.AspNetCore.nuspec
-    Copy-Item MQTTnet.Extensions.Rpc.nuspec -Destination MQTTnet.Extensions.Rpc.nuspec.old
+    Copy-Item MQTTnet.Extensions.Rpc.nuspec -Destination MQTTnet.Extensions.Rpc.nuspec.old -Force
     (Get-Content MQTTnet.Extensions.Rpc.nuspec) -replace '\$nugetVersion', $nugetVersion | Set-Content MQTTnet.Extensions.Rpc.nuspec
-    Copy-Item MQTTnet.Extensions.ManagedClient.nuspec -Destination MQTTnet.Extensions.ManagedClient.nuspec.old
+    Copy-Item MQTTnet.Extensions.ManagedClient.nuspec -Destination MQTTnet.Extensions.ManagedClient.nuspec.old -Force
     (Get-Content MQTTnet.Extensions.ManagedClient.nuspec) -replace '\$nugetVersion', $nugetVersion | Set-Content MQTTnet.Extensions.ManagedClient.nuspec
 	
 	New-Item -ItemType Directory -Force -Path .\NuGet
@@ -53,7 +53,7 @@ if ($path) {
 	.\nuget.exe pack MQTTnet.Extensions.Rpc.nuspec -Verbosity detailed -Symbols -OutputDir "NuGet" -Version $nugetVersion
     .\nuget.exe pack MQTTnet.Extensions.ManagedClient.nuspec -Verbosity detailed -Symbols -OutputDir "NuGet" -Version $nugetVersion
     
-    Copy-Item MQTTnet.AspNetCore.nuspec.old -Destination MQTTnet.AspNetCore.nuspec
-    Copy-Item MQTTnet.Extensions.Rpc.nuspec.old -Destination MQTTnet.Extensions.Rpc.nuspec
-    Copy-Item MQTTnet.Extensions.ManagedClient.nuspec.old -Destination MQTTnet.Extensions.ManagedClient.nuspec
+    Move-Item MQTTnet.AspNetCore.nuspec.old -Destination MQTTnet.AspNetCore.nuspec -Force
+    Move-Item MQTTnet.Extensions.Rpc.nuspec.old -Destination MQTTnet.Extensions.Rpc.nuspec -Force
+    Move-Item MQTTnet.Extensions.ManagedClient.nuspec.old -Destination MQTTnet.Extensions.ManagedClient.nuspec -Force
 }