Based on the work done by Peter Hutterer. Original commit message:
If SIGUSR1 is set to SIG_IGN, X servers (all of them, including Xvfb)
will send that signal to the parent process when they're ready to accept
connections. We can use that instead of a hardcoded sleep which brings
the wait down to ~37ms on my box.
The x11 test is currently silently skipped in CI, because it requires a
running X server.
Create a xvfb wrapper to run the test. We do not use `xvfb-run`, because
it is a shell script and it causes valgrind to detect unrelated memory
issues in the shell (dash, bash).
Improve wrapper using a special ELF section
TODO: The wrapper is intended to be used with the x11comp test as well.
Pierre Le Marre