Create script to set up command line build environment

eng/restore-toolset.ps1

@@ -0,0 +1,50 @@
+function InitializeCustomSDKToolset {    
+  if (-not $restore) {
+    return
+  }
+
+  # The following frameworks and tools are used only for testing.
+  # Do not attempt to install them in source build.
+  if ($env:DotNetBuildFromSource -eq "true") {
+    return
+  }
+
+  # InstallDotNetSharedFramework "1.0.5"
+  # InstallDotNetSharedFramework "1.1.2"
+  # InstallDotNetSharedFramework "2.1.0"
+
+  CreateBuildEnvScript
+}
+
+function CreateBuildEnvScript()
+{
+  Create-Directory $ArtifactsDir
+  $scriptPath = Join-Path $ArtifactsDir "core-sdk-build-env.bat"
+  $scriptContents = @"
+@echo off
+title Core SDK Build ($RepoRoot)
+set DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1
+set DOTNET_MULTILEVEL_LOOKUP=0
+
+set PATH=$env:DOTNET_INSTALL_DIR;%PATH%
+set NUGET_PACKAGES=$env:NUGET_PACKAGES
+"@
+
+  Out-File -FilePath $scriptPath -InputObject $scriptContents -Encoding ASCII
+}
+
+function InstallDotNetSharedFramework([string]$version) {
+  $dotnetRoot = $env:DOTNET_INSTALL_DIR
+  $fxDir = Join-Path $dotnetRoot "shared\Microsoft.NETCore.App\$version"
+
+  if (!(Test-Path $fxDir)) {
+    $installScript = GetDotNetInstallScript $dotnetRoot
+    & $installScript -Version $version -InstallDir $dotnetRoot -Runtime "dotnet"
+
+    if($lastExitCode -ne 0) {
+      throw "Failed to install shared Framework $version to '$dotnetRoot' (exit code '$lastExitCode')."
+    }
+  }
+}
+
+InitializeCustomSDKToolset