message: tools: add support for the -Prerelease VS locations
  take advantage of the switch parameter on the Cmdlet Get-VSSetupInstance from the vssetup module.
diff: @@ -51,7 +51,9 @@ function Import-LocalModule
  function Set-MsbuildDevEnvironment
  {
  [CmdletBinding()]
  - param()
  + param(
  + [switch]$Prerelease
  + )
  $ErrorActionPreference = 'Stop'
  @@ -59,7 +61,7 @@ function Set-MsbuildDevEnvironment
  Write-Verbose 'Searching for VC++ instances'
  $vsinfo = `
  - Get-VSSetupInstance -All `
  + Get-VSSetupInstance -All -Prerelease:$Prerelease `
  | Select-VSSetupInstance `
  -Latest -Product * `
  -Require 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64'
  