Fix ILVerify CI failure: disable UpdateXlf target for net10.0 builds (#19220)

Author: Copilot

tests/ILVerify/ilverify.ps1

@@ -29,6 +29,9 @@ Write-Host "Repository path: $repo_path"
 [string] $script = if ($IsWindows) { Join-Path $repo_path "build.cmd" } else { Join-Path $repo_path "build.sh" }
 [string] $additional_arguments = if ($IsWindows) { "-noVisualStudio" } else { "" }
 
+# Set environment variable to disable UpdateXlf target (not needed for IL verification)
+$env:UpdateXlfOnBuild = "false"
+
 # Set configurations to build
 [string[]] $configurations = @("Debug", "Release")