treewide: use mirror urls (#386594)

pkgs/by-name/ac/activemq/package.nix

···
   inherit version;
 
   src = fetchurl {
-    url = "https://archive.apache.org/dist/activemq/${version}/apache-activemq-${version}-bin.tar.gz";
+    url = "mirror://apache/activemq/${version}/apache-activemq-${version}-bin.tar.gz";
     hash = "sha256-JrLLSm6+Be1vSBTTryRcZfbiGK0PrmJ/pM2uYnGuN9E=";
   };
 

pkgs/by-name/li/libxmlxx5/package.nix

···
   version = "5.4";
 
   src = fetchurl {
-    url = "https://download.gnome.org/sources/libxml++/${version}/libxml++-${lib.versions.pad 3 version}.tar.xz";
+    url = "mirror://gnome/sources/libxml++/${version}/libxml++-${lib.versions.pad 3 version}.tar.xz";
     hash = "sha256-6aI8Q2aGqUaY0hOOa8uvhJEh1jv6D1DcNP77/XlWaEg=";
   };