Option to specify restic binary to use (restic is not in $PATH or to use different version)

[lambdaupb]

I'm using a restic binary not in $PATH, redu fails calling restic and it is not possible to override the exec path for restic.

Maybe it is worth the effort to put in a cli option for that.

It's not a huge issue, I can also edit $PATH.

[drdo]

Hello.

I think this would be useful.

Maybe something like --restic-binary and the corresponding RESTIC_BINARY env var.