apache-httpd: Strip modules

We did this for 2.2 (cc61d31902d67b94333f53a5ab5772330bbc21cc) but
lost this for 2.4. This reduces the Apache closure size from 312 MiB
to 102 MiB (primarily by getting rid of -dev outputs).

pkgs/servers/http/apache-httpd/2.4.nix

···
   preConfigure = ''
     configureFlags="$configureFlags --includedir=$dev/include"
   '';
+
   configureFlags = ''
     --with-apr=${apr.dev}
     --with-apr-util=${aprutil.dev}
···
   '';
 
   enableParallelBuilding = true;
+
+  stripDebugList = "lib modules bin";
 
   postInstall = ''
     mkdir -p $doc/share/doc/httpd