v141_xp: VS Installer whack-a-mole tournament

VS installer's startup is not instantaneous and there's some lag in the
CI/CD pipeline. Adjust strategy to wait for startup (20 seconds max) to
make the script more robust. (Doesn't seem to get triggered, but that
doesn't mean it won't happen in the future.)

Add the the following command line flags:

    --force: Forces VS instance termination, if any are running.
        (Unclear impact. Paranoia.)

    --norestart: Delay reboot, if reboot needed. (Probable reason why
        (Most likely reason why installs were incomplete.)

    --installWhileDownloading: Self-explanitory. (Unclear impact.)

"Get-VSSetupInstance/Select-VSSetupInstance" will report a VS
instance ID if successful, e.g.:

    DEBUG: Get-VSSetupInstance/Select-VSSetupInstance
    InstanceId          : 8d19910a
    DisplayName         : Visual Studio Enterprise 2022
    InstallationVersion : 17.6.33815.320
    InstallationPath    : C:\Program Files\Microsoft Visual Studio\2022\Enterprise
    InstallDate         : 6/20/2023 9:38:11 PM

Useful output in the GH CI/CD log for future debugging.

.github/workflows/cmake-builds.yml

@@ -141,35 +141,60 @@ jobs:
 
           & ${vswhere} -property installationPath | `
             Foreach-Object -process {
-              Write-Debug ("Executing: " + $vsinstaller + " " + ($Params -join " "))
-              & $vsInstaller modify --installPath "$_" --add Microsoft.VisualStudio.Component.VC.v141.x86.x64 `
-                --add Microsoft.VisualStudio.Component.WinXP --quiet `
-                2> $vsInstallErr | Write-Output
+              ## --quiet: Don't open/show UI
+              ## --force: Terminate any VS instances forcibly
+              ## --norestart: Delay reboot after install, if needed
+              ## --installWhileDownloading: Self-explanitory.
+              $Params = @(
+                  "modify",
+                  "--installPath", "$_",
+                  "--add", "Microsoft.VisualStudio.Component.VC.v141.x86.x64",
+                  "--add", "Microsoft.VisualStudio.Component.WinXP",
+                  "--quiet", "--force", "--norestart", "--installWhileDownloading"
+                  )
+
+              & $vsInstaller $Params 2> $vsInstallErr > $vsInstallOut
+
+              $vsinstallerProcesses = @('vs_installer', 'vs_installershell', 'vs_installerservice')
+              $vsInstallerStartup = $true
+              $vsInstallerStartCount = 10
 
-              Write-Debug ('Looking for running VS installer processes')
-              $vsinstallerProcesses = @('vs_installershell', 'vs_installerservice')
               do
               {
+                  Write-Debug ('Looking for running VS installer processes')
                   $vsInstallerRemaining = Get-Process -Name $vsinstallerProcesses -ErrorAction SilentlyContinue | Where-Object { $null -ne $_ -and -not $_.HasExited }
                   $vsInstallerProcessCount = ($vsInstallerRemaining | Measure-Object).Count
                   if ($vsInstallerProcessCount -gt 0)
                   {
+                      ## Installer processes are present, so obviously not starting up.
+                      $vsInstallerStartup = $false
                       try
                       {
-                          Write-Debug "Found $vsInstallerProcessCount still running Visual Studio installer processes which are known to exit asynchronously:"
+                          Write-Debug "Found $vsInstallerProcessCount running Visual Studio installer processes which are known to exit asynchronously:"
                           $vsInstallerRemaining | Sort-Object -Property Name, Id | ForEach-Object { '[{0}] {1}' -f $_.Id, $_.Name } | Write-Debug
                           Write-Debug ('Giving the processes some time to exit')
-                          $vsInstallerRemaining | Wait-Process -Timeout 1 -ErrorAction SilentlyContinue
-                          Write-Debug ('Looking for running VS installer processes')
+                          $vsInstallerRemaining | Wait-Process -Timeout 45 -ErrorAction SilentlyContinue
                       }
                       finally
                       {
                           $vsInstallerRemaining | ForEach-Object { $_.Dispose() }
                           $vsInstallerRemaining = $null
                       }
+                  } else {
+                    if ($vsInstallerStartup) {
+                      if ($vsInstallerStartCount -gt 0) {
+                        Write-Debug "No VS installer processes detected; sleeping with $vsInstallerStartCount tries remaining."
+                        Start-Sleep -Seconds 10.0
+                        $vsInstallerStartCount -= 1
+                      } else {
+                        $vsInstallerStartup = $false
+                        Write-Debug "VS installer never started? Exiting."
+                        Exit 99
+                      }
+                    }
                   }
               }
-              while ($vsInstallerProcessCount -gt 0)
+              while (($vsInstallerStartup -and $vsInstallerStartCount -gt 0) -or $vsInstallerProcessCount -gt 0)
             }
 
           if ((Test-Path $vsInstallOut -PathType Leaf) -and (Get-Item $vsInstallOut).length -gt 0kb)