The utility script installs the basic shared MiKTeX on AppVeyor builder and configures proper language support.
The utility provides only basic language support.
It's highly recommended to cache the c:\miktex directory between builds.
Binary executables are located at the following location:
c:\miktex\miktex\bin
so, the best solution would be add it to PATH:
set "PATH=%PATH%;c:\miktex\miktex\bin"