Please document per-architecture version hashes for each release

[swolchok]

Currently, it seems that I have to have access to a machine of each supported architecture I care about in order to determine the version hash output by buck2 --version for a given release. This is inconvenient; I should be able to predict the output of buck2 --version for any given release+architecture without actually running buck2.

Context: I am attempting to update ExecuTorch's buck2 version pins.

[dbort]

Fixing #345 would make this even easier; if all binaries printed a legible version number we wouldn't need to deal with hashes at all