Remove workaround for older Linux kernels

[newpavlov]

Minimum supported kernel version got bumped to 2.6.32 in rust-lang/rust#74163

[newpavlov]

CI failures look unrelated to changes in this PR.

[dhardy]

Presumably that change will appear in Rust 1.46.0, which means that in theory we should not remove this workaround until the MSRV ≥ 1.46.

On the other hand, I doubt many people actually care about using the latest getrandom on such an ancient system, so it's likely unimportant. @josephlr?

[newpavlov]

Presumably that change will appear in Rust 1.46.0

I don't think so. Libraries having stricter OS requirements than std is not unusual, e.g. think of crates which utilize io-uring. By this logic they would have MSRV which will not be released in a decade or so.

We had two reasons for the workaround: possibility of getrandom being used by std and the fact that it's part of Firefox dependency tree. Since RHEL and CentOS no longer block the update, I think we can go forward with this change. And we are being extra careful by releasing it as part of v0.2. and not v0.1.

[josephlr]

This looks good. Regarding the above comments:

• This makes Linux 2.6.23 the minimum supported kernel for getrandom 0.2
• This does not affect the MSRV, as old versions of Rust (on not-ancient kernels) will still work fine
• Having this as part of 0.2 seems correct (to avoid breakage), although ~0 people actually care
• We're making this change at the same time as Rust's libstd only because we target roughly the same support as libstd. There are no depedancies between these changes
• CI issues are unrelated (see stdweb: Remove CI runs with cargo-web #154 and rustfmt: Run cargo fmt #155)