dist: Add back arch in x64 linux AppImage (#1754)
dist: Add back arch in x64 linux AppImage (#1754)

With the recent versions of `electron-builder`, the generated AppImage
file for x64 architectures does not have `x86_64` in its name like it
used to.
We need this part in the file name for the nuts server to find it when
users want to download the app from our website.
cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop