add quick&dirty patch for cntr on aarch64

cntr/cntr-aarch64.nix

+{ cntr ? (import <nixpkgs> {}).cntr }:
+assert (cntr.version == "1.2.1");
+cntr.overrideAttrs (old: {
+  patches = [ ./cntr-aarch64.patch ];
+  patchPhase = ''
+    for patch in $patches ; do
+      ( cd ..; patch --batch -p1 <$patch )
+    done
+    sed -i s/8289b6311182176944bbf5b711b62e441d85ad9140051808ccb5fab284cf20f7/960fa52b22af210298ec997eb8c9e4124cca1a2896fbc1690cbd6850c0586fd6/ ../cntr-1.2.1-vendor.tar.gz/cntr-nix/.cargo-checksum.json
+    grep -q 960fa52b22af210298ec997eb8c9e4124cca1a2896fbc1690cbd6850c0586fd6 ../cntr-1.2.1-vendor.tar.gz/cntr-nix/.cargo-checksum.json
+  '';
+  meta = old.meta // { platforms = old.meta.platforms ++ [ "aarch64-linux" ]; };
+})

cntr/cntr-aarch64.patch

+--- a/cntr-1.2.1-vendor.tar.gz/cntr-nix/src/sys/xattr.rs.bak	2020-12-29 03:48:35.311848020 +0100
++++ b/cntr-1.2.1-vendor.tar.gz/cntr-nix/src/sys/xattr.rs	2020-12-29 04:50:43.686107763 +0100
+@@ -60,21 +60,21 @@
+ pub fn listxattr<P: ?Sized + NixPath>(path: &P, list: &mut [u8]) -> Result<usize> {
+     let res = try!(unsafe {
+         path.with_nix_path(|cstr| {
+-            libc::listxattr(cstr.as_ptr(), list.as_mut_ptr() as *mut i8, list.len())
++            libc::listxattr(cstr.as_ptr(), list.as_mut_ptr() as *mut libc::c_char, list.len())
+         })
+     });
+     Errno::result(res).map(|size| size as usize)
+ }
+ 
+ pub fn flistxattr(fd: RawFd, list: &mut [u8]) -> Result<usize> {
+-    let res = unsafe { libc::flistxattr(fd, list.as_mut_ptr() as *mut i8, list.len()) };
++    let res = unsafe { libc::flistxattr(fd, list.as_mut_ptr() as *mut libc::c_char, list.len()) };
+     Errno::result(res).map(|size| size as usize)
+ }
+ 
+ pub fn llistxattr<P: ?Sized + NixPath>(path: &P, list: &mut [u8]) -> Result<usize> {
+     let res = try!(unsafe {
+         path.with_nix_path(|cstr| {
+-            libc::llistxattr(cstr.as_ptr(), list.as_mut_ptr() as *mut i8, list.len())
++            libc::llistxattr(cstr.as_ptr(), list.as_mut_ptr() as *mut libc::c_char, list.len())
+         })
+     });
+     Errno::result(res).map(|size| size as usize)