travis: fix osx make build

This variable was removed in commit 087af992a276e7478c9c "travis: remove
unused linux code path" because it looked like it was only used by the
Linux build. Turns out I was wrong, so let's restore it.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
1 file changed