Use dotnet runner autodetect mechanism

Author: BCSharp

make.ps1

@@ -5,13 +5,12 @@ Param(
     [String] $target = "build",
     [String] $configuration = "Release",
     [String[]] $frameworks=@('net462','netcoreapp3.1','net6.0','net8.0'),
-    [String] $platform = [Runtime.InteropServices.RuntimeInformation]::ProcessArchitecture,
+    [String] $platform = $null,  # auto-detect
     [switch] $runIgnored,
     [int] $jobs = [System.Environment]::ProcessorCount
 )
 
 $ErrorActionPreference="Continue"
-if (-not $platform) { $platform = "x64"; }
 
 [int] $global:Result = 0
 [bool] $global:isUnix = [System.Environment]::OSVersion.Platform -eq [System.PlatformID]::Unix
@@ -76,12 +75,14 @@ function GenerateRunSettings([String] $framework, [String] $platform, [String] $
     $doc.AppendChild($dec) | Out-Null
 
     $runSettings = $doc.CreateElement("RunSettings")
-
+    
     $runConfiguration = $doc.CreateElement("RunConfiguration")
     $runSettings.AppendChild($runConfiguration) | Out-Null
-    $targetPlatform = $doc.CreateElement("TargetPlatform")
-    $targetPlatform.InnerText = $platform
-    $runConfiguration.AppendChild($targetPlatform) | Out-Null
+    if ($platform) {
+        $targetPlatform = $doc.CreateElement("TargetPlatform")
+        $targetPlatform.InnerText = $platform
+        $runConfiguration.AppendChild($targetPlatform) | Out-Null
+    }
 
     $testRunParameters = $doc.CreateElement("TestRunParameters")
     $runSettings.AppendChild($testRunParameters) | Out-Null