Support riscv64 architecture

[Elara6331]

Proposal

Allow Nomad to compile for riscv64 CPUs.

Use-cases

Use Nomad on riscv64 machines

Attempted Solutions

Nomad currently doesn't compile due to its dependency on raft-boltdb, which depends on the unmaintained boltdb to convert old databases to bbolt, and boltdb doesn't compile for riscv64 as well as several other platforms. hashicorp/raft-boltdb#37 uses build tags to disable the conversion features on unsupported platforms and return an error instead. If that's merged and nomad updates its dependency, that should fix this. I've built a Nomad binary with that change and it's been running without any issues for about 2 months.

[jrasell]

Hi @Elara6331 and thanks for raising this issue. It would be nice to be able to support as many architectures as possible and we appreciate the work done within Raft-BoltDB. I'll add this to our backlog, however, I cannot promise any immediate action. If anyone else comes across this issue and also would like riscv64 official releases, please give the original comments a +1.