Cleanup x64/x86 options in scripts/build-windows.bat (#2023)
* Match build-windows.bat changes
The location for manual setting of the vcvarsall.bat location moved to line 38 in the latest change.
* Update flags for clean x64/x86 building
std:c11 is required for initialization features used in raylib. UTF-8 for consistency in contemporary systems. /W3 gets rid of puzzling slack byte and linker in-lining warnings. /sdl for some insecure library usages in the user code that beginners should learn about early.