win,msi: install Boxstarter from elevated shell

Boxstarter asks for elevation to install packages, but not to install
Boxstarter itself. Thus, run all the commands from an elevated
PowerShell.

Refs: nodejs#22645
PR-URL: nodejs#22988
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

tools/msvs/install_tools/install_tools.bat

@@ -22,4 +22,4 @@ echo available at https://github.com/nodejs/node-gyp#on-windows
 echo.
 pause
 
-"%SystemRoot%\System32\WindowsPowerShell\v1.0\powershell.exe" -NoProfile -InputFormat None -ExecutionPolicy Bypass -Command "iex ((New-Object System.Net.WebClient).DownloadString('https://boxstarter.org/bootstrapper.ps1')); get-boxstarter -Force; Install-BoxstarterPackage -PackageName '%~dp0\install_tools.txt'"
+"%SystemRoot%\System32\WindowsPowerShell\v1.0\powershell.exe" -NoProfile -InputFormat None -ExecutionPolicy Bypass -Command Start-Process '%SystemRoot%\System32\WindowsPowerShell\v1.0\powershell.exe' -ArgumentList '-NoProfile -InputFormat None -ExecutionPolicy Bypass -Command iex ((New-Object System.Net.WebClient).DownloadString(''https://boxstarter.org/bootstrapper.ps1'')); get-boxstarter -Force; Install-BoxstarterPackage -PackageName ''%~dp0\install_tools.txt''; Read-Host ''Type ENTER to exit'' ' -Verb RunAs