Update build and fix a couple of things

1. Update to use .NET SDK 8.0.406
2. Set the execution permission to 'aish' on Linux and macOS before packaging
3. Sign Azure agent assembly with the 1st-party certificate

Author: daxian-dbw

build.psm1

@@ -336,7 +336,7 @@ function Copy-1PFilesToSign
         [string] $TargetRoot
     )
 
-    $pattern = "*.ps*1", "AIShell.*.dll", "aish.dll", "aish.exe", "Markdown.VT.dll", "ReadLine.dll"
+    $pattern = "*.ps*1", "AIShell.*.dll", "aish.dll", "aish.exe", "Markdown.VT.dll", "ReadLine.dll", "Microsoft.Azure.Agent.dll"
 
     if (Test-Path $TargetRoot) {
         Remove-Item -Path $TargetRoot -Recurse -Force

global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": "8.0.403"
+    "version": "8.0.406"
   }
 }

tools/packaging/packaging.psm1

@@ -148,6 +148,15 @@ function New-TarballPackage
         }
     }
 
+    if (Get-Command -Name chmod -CommandType Application -ErrorAction Ignore) {
+        Write-Verbose "Add the execution permission to 'aish'" -Verbose
+        $executable = Join-Path $PackageSourcePath 'aish'
+        chmod +x $executable
+
+        $permission = Get-ChildItem $executable | ForEach-Object UnixFileMode
+        Write-Verbose "File permission: $permission" -Verbose
+    }
+
     if (Get-Command -Name tar -CommandType Application -ErrorAction Ignore) {
         Write-Verbose "Create tarball package" -Verbose
         $options = "-czf"