timeshift: Fix GCC 14 build

TeeJee.Process.c:1134:9: error: implicit declaration of function 'kill'

+4
+4
pkgs/applications/backup/timeshift/unwrapped.nix
··· 57 57 xapp 58 58 ]; 59 59 60 + env = lib.optionalAttrs stdenv.cc.isGNU { 61 + NIX_CFLAGS_COMPILE = "-Wno-error=implicit-function-declaration"; 62 + }; 63 + 60 64 meta = with lib; { 61 65 description = "System restore tool for Linux"; 62 66 longDescription = ''