FUSE SafeHardlinkOps filesystem doesn't work on ppc64

I was hitting strange errors running BuildStream on a ppc64 machine, where integration commands and bst shell would fail with execvp sh: Exec format error.

This turned out to be because fusepy didn't know the struct stat layout on that architecture and so was falling back to the layout it uses on i686 platforms, causing all sorts of crazy behaviour from the safe-hardlinks filesystem.

I've sent a pull request for fusepy to fix this issue: https://github.com/terencehonles/fusepy/pull/72

However, the project seems inactive and since it's only one file it might make more sense to bundle the file with BuildStream. Without this fix BuildStream is basically unusable on powerpc64 machines.