Properly check return of Invoke-Expression

In cibuild-legacy.ps1 we cannot use Exec-Expression because it's a
bootstrapping problem.  Hence we have to use Invoke-Expression directly.

Even though we invoke a script via Invoke-Expression here we still must
check $LastExitCode.  In the case where the script exits explicitly with
an exit code this doesn't actually cause $? to be $false.  Hence we
still must check both values here.

build/scripts/cibuild-legacy.ps1

@@ -25,4 +25,7 @@ Write-Host "!!!This script is legacy and will be deleted.  Please call build/scr
 Write-Host "New Args are $newArgs"
 $script = Join-Path $PSScriptRoot "cibuild.ps1"
 Invoke-Expression "$script $newArgs"
+if ((-not $?) -or ($lastexitcode -ne 0)) {
+    exit 1
+} 
 Write-Host "!!!This script is legacy and will be deleted.  Please call build/scripts/cibuild.cmd directly!!!"