tools,win: refactor install_tools.bat

* Ask for credentials upfront
* Try to `-DisableReboots`

tools/msvs/install_tools/install_tools.bat

@@ -73,4 +73,4 @@ if /i not "%ACCEPT_PROMPT%"=="yes" (
   goto acceptretry
 )
 
-"%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
+"%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 -File "%~dp0\install_tools.ps1"' -Verb RunAs

tools/msvs/install_tools/install_tools.ps1

@@ -0,0 +1,23 @@
+try
+{
+  $PSScriptRoot = Split-Path $MyInvocation.MyCommand.Path -Parent;
+
+  # Ask for an opaque user credentials token
+  $cred = Get-Credential $( whoami ) -Message "The Node.js installer needs your credentials to streamline the installation of the Build Tools";
+  if (!($cred)) {
+    # Wait for user confirmation.
+    Echo 'The installer will now exit.';
+    Read-Host 'Press ENTER to finish';
+    exit 1;
+  }
+  # The following line is lifted verbatim from https://boxstarter.org/InstallBoxstarter
+  iex ((New-Object System.Net.WebClient).DownloadString('https://boxstarter.org/bootstrapper.ps1')); get-boxstarter -Force;
+
+  # Install the packges from `install_tools.txt`
+  Install-BoxstarterPackage -PackageName ($PSScriptRoot+'\install_tools.txt') -Credential $cred -DisableReboots;
+
+  # Wait for user confirmation.
+  Read-Host 'Press ENTER to finish';
+} catch {
+  exit 1;
+}