Fix cross-platform test launcher

Author: Copilot

run-tests.ps1

@@ -6,10 +6,28 @@ param(
 
 Set-StrictMode -Version Latest
 $ErrorActionPreference = 'Stop'
+$env:DOTNET_ROLL_FORWARD = 'Major'
+
+$DotNet = if ($IsWindows) {
+    "$PSScriptRoot/eng/common/dotnet.ps1"
+} else {
+    "$PSScriptRoot/eng/common/dotnet.sh"
+}
+$DotNetArgs = @(
+    'run'
+    '--project'
+    'Microsoft.DotNet.BuildTools.Prereqs.Docker.Tests.csproj'
+    '--report-xunit-trx'
+    '--results-directory'
+    "$PSScriptRoot/artifacts/TestResults"
+)
+if ($OptionalArgs) {
+    $DotNetArgs += $OptionalArgs
+}
 
 Push-Location "$PSScriptRoot/tests/Microsoft.DotNet.BuildTools.Prereqs.Docker.Tests"
 try {
-    & "$PSScriptRoot/eng/common/dotnet.ps1" run --project Microsoft.DotNet.BuildTools.Prereqs.Docker.Tests.csproj --report-xunit-trx --results-directory $PSScriptRoot/artifacts/TestResults $OptionalArgs
+    & $DotNet @DotNetArgs
 
     if ($LASTEXITCODE -ne 0) {
         throw "Failed: dotnet run Microsoft.DotNet.BuildTools.Prereqs.Docker.Tests"