rustc: Spawn `cmd /c` for `.bat` scripts
rustc: Spawn `cmd /c` for `.bat` scripts

This fixes an accidental regression #46335 where the behavior of
`Path::ends_with` is different from `str::ends_with` (paths operate over
components, strs operate over chars).

aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust