message: metrics: switch to cfg(target_os = "linux")
diff: @@ -31,10 +31,10 @@ metrics! {
  pub(crate) failed_db_connections: IntCounter,
  /// The number of currently opened file descriptors
  - #[cfg(linux)]
  + #[cfg(target_os = "linux")]
  open_file_descriptors: IntGauge,
  /// The number of threads being used by docs.rs
  - #[cfg(linux)]
  + #[cfg(target_os = "linux")]
  running_threads: IntGauge,
  /// The traffic of various docs.rs routes
  @@ -86,10 +86,10 @@ impl Metrics {
  Ok(self.registry.gather())
  }
  - #[cfg(not(linux))]
  + #[cfg(not(target_os = "linux"))]
  fn gather_system_performance(&self) {}
  - #[cfg(linux)]
  + #[cfg(target_os = "linux")]
  fn gather_system_performance(&self) {
  use procfs::process::Process;
  