on a freshly installed environment diff.exe requires newer runtime
dll's. For now only fix this on X64 as on windows on arm there's
issues with newer msys2 versions (but I do now know exactly what
they are anthony has brought it up in the past) this can however
not remain in a broken state, so fixing it for X64 only.
Also fix typo in download_package function
These two fixes together should bring a fresh vmprep install back
to working order.
73c751afaf