Build script with vergen collecting system info might take a lot of time

[akoptelov]

With current usage in vergen crate, sysinfo accesses all filesystems on the host. If there is a network filesystem that cannot be mounted (e.g. it is in a different network), sysinfo's System::new_all() might be stuck for some time.

In my case, this is automount entries with content from my NAS server that causing the issue.

How to reproduce (currently inaccessible network filesystem should exist):
Within a rust project (e.g. created with cargo new vergen-sysinfo-test), create a build.rs with the following content:

fn main() -> Result<(), Box<dyn std::error::Error>> {
    vergen::EmitBuilder::builder().all_sysinfo().emit_and_set()?;
    Ok(())
}

and run

cargo build --verbose