add windows build script

build.bat

@@ -0,0 +1,10 @@
+@echo off
+fasm kernel\boot\bootx64.asm
+if errorlevel 1 (
+    echo build failed
+    exit /b 1
+)
+rd /s /q image
+mkdir image\EFI\BOOT
+copy kernel\boot\bootx64.efi image\EFI\BOOT\
+qemu-system-x86_64 -cpu qemu64 -bios OVMF.fd -drive driver=vvfat,rw=on,dir=image\