Fix test sample launch environment.

BUG=18313324

Change-Id: I21c2ec40eb9f3a12691b68d3d3bb3df9a2e2b58c
Reviewed-on: https://swiftshader-review.googlesource.com/1358
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>