build without sdl for travis

configure

@@ -1,9 +1,11 @@
 #!/usr/bin/env bash
-set -ex
+set -e
+interactive_pkgs=libsdl2-dev
 y=''
 while getopts t OPT; do
   case "$OPT" in
     t)
+      interactive_pkgs=''
       y='-y'
       ;;
   esac
@@ -21,6 +23,6 @@ sudo apt-get update $y
 sudo apt-get install $y \
   build-essential \
   coreutils \
-  libsdl2-dev \
+  $interactive_pkgs \
 ;
 sudo apt-get build-dep $y qemu