Update sysinfo to 0.30.8

[Hoverbear]

Fixes a Mac specific issue when using metrics = true in config.toml.

# Collect information and statistics about the current build and writes it to
# disk. Enabling this or not has no impact on the resulting build output. The
# schema of the file generated by the build metrics feature is unstable, and
# this is not intended to be used during local development.
metrics = true

During repeated builds, as the generated metrics.json grew, eventually refresh_cpu() would be called in quick enough succession (specifically: under 200ms) that a divide by zero would occur, leading to a NaN which would not be serialized, then when the metrics.json was re-read it would fail to parse.

That error looks like this (collected from Ferrocene's CI):

   Compiling rustdoc-tool v0.0.0 (/Users/distiller/project/src/tools/rustdoc)
    Finished release [optimized] target(s) in 38.37s
thread 'main' panicked at src/utils/metrics.rs:180:21:
serde_json::from_slice::<JsonRoot>(&contents) failed with invalid type: null, expected f64 at line 1 column 9598
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Build completed unsuccessfully in 0:00:40

Exited with code exit status 1

Related: GuillaumeGomez/sysinfo#1236

[rustbot]

r? @Mark-Simulacrum

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[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[Noratrieb]

@bors r+ rollup

[bors]

📌 Commit b626f01 has been approved by Nilstrieb

It is now in the queue for this repository.