Fix GH-2641: ptrace with unsigned int is only for uclibc/Linux glibc.

Author: devnexen

src/sys/ptrace/linux.rs

@@ -24,7 +24,7 @@ pub type AddressType = *mut ::libc::c_void;
 use libc::user_regs_struct;
 
 cfg_if! {
-    if #[cfg(any(all(target_os = "linux", target_arch = "s390x"),
+    if #[cfg(any(
                  all(target_os = "linux", target_env = "gnu"),
                  target_env = "uclibc"))] {
         #[doc(hidden)]