Add PowerShell build script as alternative to cmd

xb.ps1

@@ -0,0 +1,24 @@
+function Write-FatalError($message) {
+    [Console]::ForegroundColor = 'red'
+    [Console]::Error.WriteLine($message)
+    [Console]::ResetColor()
+    Exit 1
+}
+
+$pythonPath = Get-Command python | Select-Object -ExpandProperty Definition
+
+# Check for 'python3' if 'python' isn't found
+if ([string]::IsNullOrEmpty($pythonPath)) {
+    $pythonPath = Get-Command python3 | Select-Object -ExpandProperty Definition
+}
+# Neither found, error and exit
+if ([string]::IsNullOrEmpty($pythonPath)) {
+    Write-FatalError "ERROR: no Python executable found on PATH.`nMake sure you can run 'python' or 'python3' in a Command Prompt."
+}
+
+python -c "import sys; sys.exit(1 if not sys.version_info[:2] >= (3, 4) else 0)"
+if ($LASTEXITCODE -gt 0) {
+    Write-FatalError "ERROR: Python version mismatch, not at least 3.4.`nFound Python executable was $($pythonPath)"
+}
+
+python "$($PSScriptRoot)/xenia-build" $args