bad exit status doesn't propagate in build command

[cireu]

In https://github.com/akermu/emacs-libvterm/blob/master/vterm.el#L103, the build commands are connecting with ;. However, if one of these commands(unless last one) fails, shell will still return 0 as exit code. This is the default behaviour of bash (Unless you use set -e)

I suggest use && to connect commands, forcing all of them to execute successfully.