max_jobs: default to 2 if we can't compute it, use ceil instead of floor

devenv/src/cli.rs

@@ -351,7 +351,7 @@ fn max_jobs() -> u8 {
  eprintln!("Failed to get number of logical CPUs: {}", e);
  std::num::NonZeroUsize::new(4).unwrap()
  });
- num_cpus.get().div_ceil(2) as u8
+ std::cmp::max(num_cpus.get().div_ceil(2), 2) as u8
 }
 
 #[cfg(test)]