travis: add linux x64 build script

travis/build-linux_x64.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+RECIPE=recipes/linux/cores-linux-x64-generic
+
+cd ~/libretro-super
+
+# only build the one core specified in $CORE
+egrep "^$CORE " ${RECIPE} | head -1 >${RECIPE}.new && mv ${RECIPE}.new ${RECIPE}
+
+./libretro-buildbot-recipe.sh ${RECIPE}