Try chmod update.exe for linux systems test

src/vpk/Velopack.Core/Chmod.cs

@@ -2,7 +2,7 @@
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 
-namespace Velopack.Packaging.Unix;
+namespace Velopack.Core;
 
 public class Chmod
 {

test/Velopack.Packaging.Tests/CrossCompile.cs

@@ -1,4 +1,5 @@
-using Velopack.Packaging.Unix;
+using Velopack.Core;
+using Velopack.Packaging.Unix;
 using Velopack.Util;
 
 namespace Velopack.Packaging.Tests;

test/Velopack.Tests/UpdateManagerTests.cs

@@ -547,6 +547,7 @@ public class UpdateManagerTests
         File.Copy(basePkgFixturePath, basePkgPath);
 
         var updateExe = PathHelper.CopyUpdateTo(packagesDir);
+        Chmod.ChmodFileAsExecutable(updateExe);
         var locator = new TestVelopackLocator(
             id,
             fromVersion,