Squid: remove --march=native

The Squid build default behaivour is to request optimisation for the
current CPU which is not a good idea in distro builds.

pkgs/servers/squid/squids.nix

···
       sha256 = "3e54ae3ad09870203862f0856c7d0cca16a85f62d5012085009003ee3d5467b4";
     };
 
-    configureFlags = ["--enable-ipv6" "--disable-strict-error-checking"];
+    configureFlags = ["--enable-ipv6" "--disable-strict-error-checking" "--disable-arch-native"];
 
     meta = {
       description = "http-proxy";