On various tested platforms (RPI3, qemu, and likely others) Weston fails to load after second or third boot with this message.

 # cat /run/platform/display/weston.log
Date: 2017-05-16 UTC
[23:23:17.360] weston 1.11.0
http://wayland.freedesktop.org
Bug reports to: https://bugs.freedesktop.org/enter_bug.cgi?product=Wayland&component=weston&version=1.11.0
Build: 1.10.93-2-g2d825ed configure.ac: bump to version 1.11.0 for the official release (2016-05-31 17:10:40 -0700)
[23:23:17.360] OS: Linux, 4.4.50, #1 SMP Tue May 16 23:43:56 UTC 2017, armv7l
[23:23:17.360] warning: XDG_RUNTIME_DIR "/run/platform/display" is not configured
correctly. Unix access mode must be 0700 (current mode is 770),
and must be owned by the user (current owner is UID 200).
Refer to your distribution on how to get it, or
http://www.freedesktop.org/wiki/Specifications/basedir-spec
on how to implement it.
[23:23:17.409] Using config file '/etc/xdg/weston/weston.ini'
[23:23:17.461] Output repaint window is 7 ms maximum.
[23:23:17.481] Loading module '/usr/lib/weston/drm-backend.so'
[23:23:17.638] initializing drm backend
[23:23:17.647] logind: not running in a systemd session
[23:23:17.647] logind: cannot setup systemd-logind helper (-6), using legacy fallback
[23:23:17.652] couldn't open /dev/dri/card0, skipping
[23:23:17.652] failed to initialize kms
[23:23:17.710] fatal: failed to create compositor backend

This can be worked around with adding the line to the weston.service:

ExecStartPre=/bin/chmod 700 /run/platform/display