p7zip: Make unfree features (rar support) optional

pkgs/tools/archivers/p7zip/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl }:
+{ stdenv, fetchurl, lib, enableUnfree ? false }:
 
 stdenv.mkDerivation rec {
   pname = "p7zip";
@@ -24,7 +24,7 @@ stdenv.mkDerivation rec {
     substituteInPlace makefile.machine \
       --replace 'CC=gcc'  'CC=${stdenv.cc.targetPrefix}gcc' \
       --replace 'CXX=g++' 'CXX=${stdenv.cc.targetPrefix}g++'
-  '' + ''
+  '' + lib.optionalString (!enableUnfree) ''
     # Remove non-free RAR source code
     # (see DOC/License.txt, https://fedoraproject.org/wiki/Licensing:Unrar)
     rm -r CPP/7zip/Compress/Rar*
@@ -50,6 +50,6 @@ stdenv.mkDerivation rec {
     platforms = stdenv.lib.platforms.unix;
     maintainers = [ stdenv.lib.maintainers.raskin ];
     # RAR code is under non-free UnRAR license, but we remove it
-    license = stdenv.lib.licenses.lgpl2Plus;
+    license = if enableUnfree then lib.licenses.unfree else lib.licenses.lgpl2Plus;
   };
 }