Installations missing some rights

Some installations, for example https://github.com/compiler-explorer/infra/pull/627
are missing rights for someone else but the installing user to access the folder.

This is probably fine for our regular NFS access to the efs drive (?), but it's weird to not be able to access it from the admin node as the non-root user.

We could consider changing the chmod that we do https://github.com/compiler-explorer/infra/blob/main/bin/lib/installation.py#L193 to a more inclusive set. (aka 0755)