event-loop: always dispatch checked sources after idle sources

wl_event_loop_dispatch dispatches idle sources before blocking.
Idle sources may perform actions that require dispatching sources
marked with wl_event_source_check. For instance, sending Wayland
requests to a remote compositor will push bytes to libwayland's
outgoing buffer. However wl_event_loop_dispatch will then block
without flushing the bytes to the FD.

To fix this, call post_dispatch_check before blocking if any idle
source was triggered.

Signed-off-by: Simon Ser <contact@emersion.fr>
Closes: wayland/wayland#187
3 jobs for fix-event-source-checked-idle in 1 minute and 18 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Prep
passed #6463432
debian:buster@container-prep

00:00:09

 
  Build
passed #6463433
build-native-autotools

00:01:09

passed #6463434
build-native-meson

00:00:20