bspwm: add _JAVA_AWT_WM_NONREPARENTING=1

bspwm is not in java's internal list of non-reparrenting
window managers. See https://awesomewm.org/wiki/Problems_with_Java

nixos/modules/services/x11/window-managers/bspwm.nix

@@ -38,6 +38,7 @@ in
       start = if cfg.startThroughSession
         then cfg.sessionScript
         else ''
+            export _JAVA_AWT_WM_NONREPARENTING=1
             SXHKD_SHELL=/bin/sh ${pkgs.sxhkd}/bin/sxhkd -f 100 &
             ${pkgs.bspwm}/bin/bspwm
         '';