opensc: remove obsolete DESTDIR patch

This patch was actively causing harm, because it lead to a "double prefix"
issue where the etc files were installed into $out/$out/etc instead of just
$out/etc.

pkgs/tools/security/opensc/default.nix

@@ -14,10 +14,6 @@ stdenv.mkDerivation rec {
     sha256 = "16y3ryx606nry2li05hm88bllrragdj3sfl3yh7pf71777n4lsk4";
   };
 
-  postPatch = ''
-    sed -i 's,$(DESTDIR),$(out),g' etc/Makefile.am
-  '';
-
   buildInputs = [
     autoreconfHook pkgconfig zlib readline openssl pcsclite libassuan
     libXt libxslt libiconv docbook_xml_dtd_412
@@ -38,9 +34,11 @@ stdenv.mkDerivation rec {
   ];
 
   installFlags = [
-    "sysconfdir=\${out}/etc"
+    "sysconfdir=$(out)/etc"
   ];
 
+  
+
   meta = with stdenv.lib; {
     description = "Set of libraries and utilities to access smart cards";
     homepage = https://github.com/OpenSC/OpenSC/wiki;