[Snek] [keith-packard/snek] 9265bd: test: Use SNEK variable to find snek binary

[Keith Packard]

  Branch: refs/heads/master
  Home:   https://github.com/keith-packard/snek
  Commit: 9265bdd6aa40085e5324081c024521ff3c0cd375
      https://github.com/keith-packard/snek/commit/9265bdd6aa40085e5324081c024521ff3c0cd375
  Author: Keith Packard <keithp at keithp.com>
  Date:   2019-03-09 (Sat, 09 Mar 2019)

  Changed paths:
    M test/Makefile

  Log Message:
  -----------
  test: Use SNEK variable to find snek binary

This should let the debian tests use the installed version

Signed-off-by: Keith Packard <keithp at keithp.com>