Use getrandom for randomness

[ChrisDenton]

The reason getrandom isn't currently used is given by:

jobserver-rs/src/windows.rs

Lines 71 to 76 in f494d82

	// Note that we ideally would use the `getrandom` crate, but unfortunately
	// that causes build issues when this crate is used in rust-lang/rust (see
	// rust-lang/rust#65014 for more information). As a result we just inline
	// the pretty simple Windows-specific implementation of generating
	// randomness.
	fn getrandom(dest: &mut [u8]) -> io::Result<()> {

which says getrandom can't be used due to rust-lang/rust#65014 which was closed as an instance of rust-lang/cargo#4866 which is closed in favour of a nightly cargo feature rust-lang/cargo#7915 which has since been stabilised.

So I think we're good now.

[weihanglo]

Reasonable. Thanks!

[clubby789]

@weihanglo Would it be possible to get a new release of jobserver with this? It should unblock this dependency bump

[weihanglo]

jobserver@0.1.33 is out.