Do not include x11 files in case of Ozone builds

This only fails when no X11 headers are present on the system and

  use_ozone = true
  ozone_platform_wayland = true
  ozone_platform_x11 = false
  use_sysroot = false

BUG=295089

Review-Url: https://codereview.chromium.org/2892343002
Cr-Commit-Position: refs/heads/master@{#473718}
1 file changed