win32 gpoll: Fix wait for at least one thread to return

When timeout grater than 0 in g_poll function, the WaitForMultipleObjects
call will wait for all the threads to return, but when only one thread
got an event the others will sleep until the timeout elapses, and causes
a stall. Triggering the stop event in g_poll in this case is useless as
it is triggered when all the threads where already signaled or timed-out.

Closes: GNOME/glib#2107
15 jobs for fix-2107-windows-gpoll-stall in 41 minutes and 9 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Style Check
passed #726341
check-todos

00:03:14

passed #726340
style-check-diff

00:03:14

 
  Build
passed #726346
cross-android_api21_arm64

00:04:44

passed #726347
cross-android_api28_arm64

00:04:24

passed #726348
cross-mingw64

00:06:33

passed #726343
debian-stable-x86_64

00:05:54

passed #728922
fedora-x86_64

00:10:43

passed #726345
G_DISABLE_ASSERT

00:06:29

passed #726344
installed-tests

00:08:11

passed #726349
win32-ps
msys2-mingw32

00:10:20

passed #726350
win32-ps
vs2017-x64

00:08:24

failed #726342
fedora-x86_64

00:16:54

 
  Coverage
passed #726351
coverage

00:01:23

78.1%
 
  Analysis
passed #726353
scan-build

00:15:25

failed #726352
allowed to fail
valgrind

00:12:21

 
Name Stage Failure
failed
valgrind Analysis
Uploading artifacts...
_build/config.h: found 1 matching files

_build/glib/glibconfig.h: found 1 matching files

_build/meson-logs: found 7 matching files

Uploading artifacts to coordinator... ok
id=726352 responseStatus=201 Created token=_AWG-NnY
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=726352 responseStatus=201 Created token=_AWG-NnY
ERROR: Job failed: exit code 1