message: disentangle macos and linux dlsyms
diff: @@ -15,15 +15,18 @@ impl Dlsym {
  use self::Dlsym::*;
  let name = String::from_utf8_lossy(name);
  Ok(match target_os {
  - "linux" | "macos" => match &*name {
  - "getentropy" => Some(GetEntropy),
  + "linux" => match &*name {
  "__pthread_get_minstack" => None,
  - _ => throw_unsup_format!("unsupported dlsym: {}", name),
  + _ => throw_unsup_format!("unsupported Linux dlsym: {}", name),
  + }
  + "macos" => match &*name {
  + "getentropy" => Some(GetEntropy),
  + _ => throw_unsup_format!("unsupported macOS dlsym: {}", name),
  }
  "windows" => match &*name {
  "SetThreadStackGuarantee" => None,
  "AcquireSRWLockExclusive" => None,
  - _ => throw_unsup_format!("unsupported dlsym: {}", name),
  + _ => throw_unsup_format!("unsupported Windows dlsym: {}", name),
  }
  os => bug!("dlsym not implemented for target_os {}", os),
  })
  