errno: simplify

hosts/common/programs/errno.nix

@@ -2,14 +2,15 @@
 {
   sane.programs.errno = {
     # packageUnwrapped = pkgs.linkIntoOwnPackage pkgs.moreutils "bin/errno";
-    # actually, don't build all of moreutils because not all of it builds for cross targets
+    # actually, don't build all of moreutils because not all of it builds for cross targets.
+    # some of this can be simplified after <https://github.com/NixOS/nixpkgs/pull/316446>
     packageUnwrapped = pkgs.moreutils.overrideAttrs (base: {
-      makeFlags = [
+      makeFlags = (base.makeFlags or []) ++ [
         "BINS=errno"
         "MANS=errno.1"
         "PERLSCRIPTS=errno"  #< Makefile errors if empty, but this works :)
+        "INSTALL_BIN=install"
       ];
-      installFlags = base.installFlags ++ [ "INSTALL_BIN=install" ];  #< cross fix; defaults `install -s`
       #v disable the perl-specific stuff
       propagatedBuildInputs = [];
       postInstall = "";