Set ozone_platform_wayland to true for ozone/ChromeOS builds

After [1], sysroots have the required dependencies installed
to get ozone/wayland builds going as part of the ozone/chromeos
buildbot - namely chromium_chromeos_ozone_rel_ng.

[1] https://codereview.chromium.org/2415933004/

BUG=295089

Review-Url: https://chromiumcodereview.appspot.com/2423833002
Cr-Commit-Position: refs/heads/master@{#426238}
1 file changed