Add linux and freebsd restriction

Author: Fensteer

src/sys/socket/sockopt.rs

@@ -10,6 +10,7 @@ use std::ffi::{CStr, CString};
 
 // Constants
 // TCP_CA_NAME_MAX isn't defined in user space include files
+#[cfg(any(target_os = "freebsd", target_os = "linux"))] 
 const TCP_CA_NAME_MAX: usize = 16;
 
 /// Helper for implementing `SetSockOpt` for a given socket option. See