Add Windows wrappers for ./y

y.cmd

@@ -0,0 +1,9 @@
+@echo off
+echo [BUILD] build system >&2
+mkdir build 2>nul
+rustc build_system/main.rs -o build\y.exe -Cdebuginfo=1 --edition 2021 || goto :error
+build\y.exe %* || goto :error
+goto :EOF
+
+:error
+exit /b

y.ps1

@@ -0,0 +1,12 @@
+$ErrorActionPreference = "Stop"
+
+$host.ui.WriteErrorLine("[BUILD] build system")
+New-Item -ItemType Directory -Force -Path build | Out-Null
+& rustc build_system/main.rs -o build\y.exe -Cdebuginfo=1 --edition 2021
+if ($LASTEXITCODE -ne 0) {
+    exit $LASTEXITCODE
+}
+& build\y.exe $args
+if ($LASTEXITCODE -ne 0) {
+    exit $LASTEXITCODE
+}