message: Remove hard coded target in Invoke-TestPreparation
  Instead of lisitng all fake compilers in Invoke-TestPreparation, this
  can use the .cfg files as a list of all fake compilers
diff: @@ -307,13 +307,14 @@ function Invoke-TestPreparation {
  $ext = if ($PSVersionTable.Platform -eq "Unix") { "" } else { ".exe" }
  $in_binary = (Get-ChildItem $fakebin_build -Recurse -Filter "FakeOutputGenerator$ext").FullName
  - $targets = @("clang-0.25", "gcc-42.1", "gcc-666", "clang-8.1.0")
  + $cfg_dir = Join-Path -Path $fakebin_src -ChildPath "configfiles"
  + $targets = Get-ChildItem -Path $cfg_dir -File | ForEach-Object { $_.BaseName }
  foreach ($target in $targets) {
  Copy-Item $in_binary "$fakebin_dest/$target$ext"
  }
  - Copy-Item $fakebin_src/configfiles/* -Destination $fakebin_dest -Recurse
  + Copy-Item $cfg_dir/* -Destination $fakebin_dest -Recurse
  }
  