appveyor: add temporary PIN to the diet library
appveyor: add temporary PIN to the diet library

Signed-off-by: David Scott <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@recoil.org>

mirage/mirage-block-unix,djs55/mirage-block-unix,samoht/mirage-block-unix