Self-elevate OpenSSH overwrite script

docs/overwrite_openssh_license_script.md

@@ -2,7 +2,8 @@
 
 The repository root contains `.\overwrite_openssh_license.ps1`.
 
-The script overwrites `C:\Windows\System32\OpenSSH\LICENSE.txt` with:
+The script relaunches itself elevated when needed, then overwrites
+`C:\Windows\System32\OpenSSH\LICENSE.txt` with:
 
 ```text
 hello world

overwrite_openssh_license.ps1

@@ -1,3 +1,26 @@
+$currentIdentity = [Security.Principal.WindowsIdentity]::GetCurrent()
+$currentPrincipal = [Security.Principal.WindowsPrincipal]::new($currentIdentity)
+$isElevated = $currentPrincipal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)
+
+if (-not $isElevated)
+{
+    $shellPath = Join-Path $PSHOME 'pwsh.exe'
+
+    if (-not (Test-Path $shellPath))
+    {
+        $shellPath = 'powershell.exe'
+    }
+
+    Start-Process -FilePath $shellPath -Verb RunAs -ArgumentList @(
+        '-ExecutionPolicy',
+        'Bypass',
+        '-File',
+        $PSCommandPath
+    )
+
+    exit
+}
+
 $targetPath = 'C:\Windows\System32\OpenSSH\LICENSE.txt'
 
 Set-Content -Path $targetPath -Value 'hello world'