qbittorrent: partial revert of 1d78f31b765f8e3fe81d79f5bc9ae381271094da

It still fails on 32bit:
http://hydra.nixos.org/build/25460116/nixlog/1/raw

(cherry picked from commit 57391b7322d97aa03158c730aec318cb0e8d2b2d)
Signed-off-by: Domen Kožar <[e-mail]>

pkgs/applications/networking/p2p/qbittorrent/default.nix

···
     (if webuiSupport then "" else "--disable-webui")
   ] ++ optional debugSupport "--enable-debug";
 
-  enableParallelBuilding = true;
+  # https://github.com/qbittorrent/qBittorrent/issues/1992 
+  enableParallelBuilding = false;
 
   meta = {
     description = "Free Software alternative to µtorrent";