Fix incorrect path usage in generate_projects. We should use the cross-platform os.path.join() to support platforms other than Windows. BUG=angle:577 Change-Id: I9d96fc1b13731a57ffcd97469632f0acedb8e5c7 Reviewed-on: https://chromium-review.googlesource.com/188879 Reviewed-by: Zhenyao Mo <zmo@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Shannon Woods <shannonwoods@chromium.org> Conflicts: generate_projects Change-Id: I76cacb8ee3acf477c0e99cd73cf91622efc3c9b4 Reviewed-on: https://chromium-review.googlesource.com/189131 Tested-by: Shannon Woods <shannonwoods@chromium.org> Reviewed-by: Zhenyao Mo <zmo@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>