bug#56487: xgselect race condition leading to abort when USE_GTK not defined

[Tom Gillespie <tgbugs@gmail.com>]

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For the record, while I was hunting a better repro for
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=56488
I had the following abort happen when built with gtk3,
so it seems that there are other conditions that can
trigger the abort in the gtk3 code path as well. The
sequence of events is attached.

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tom@host ~ $ ~/git/NOFORK/emacs/src/emacs -Q -batch -l ~/ni/sparc/prrequaestor.el -- --user-emacs-directory /tmp/lol2 --build-dir /tmp/test-build-dir --user-init-file ~/.emacs.d/prm-init.el --fun nif-scr --debug --specs ~/ni/sparc/sync-specs.el 
Loading /home/tom/.emacs.d/prm-init.el (source)...
../../tmp/lol2/elpa/bind-key-20210210.1609/bind-key.el: Warning: Use keywords rather than deprecated positional arguments to `define-minor-mode'
Loading /home/tom/ni/sparc/sync-specs.el (source)...
we get here
Pulling SciCrunch/NIF-Ontology...done
Storing SciCrunch/NIF-Ontology...
Storing SciCrunch/NIF-Ontology...done
existing-pull-requests: ((automated-sct-2022-07-10T2324Z))
stash and pull ...
running command ...
    (lambda nil
      (message "we get here too")
      (ow-run-command
       (python-impl)
       "-m" "nifstd_tools.scr_sync" "--git-local" prm-build-dir "--host" "localhost" "--port" "33060"))
    
we get here too
**
GLib:ERROR:../glib-2.72.3/glib/gmain.c:3489:g_main_context_acquire: assertion failed: (context->owner_count == 0)
Bail out! GLib:ERROR:../glib-2.72.3/glib/gmain.c:3489:g_main_context_acquire: assertion failed: (context->owner_count == 0)
Fatal error 6: Aborted
Backtrace:
/home/tom/git/NOFORK/emacs/src/emacs(+0x19a675)[0x563fa91a3675]
/home/tom/git/NOFORK/emacs/src/emacs(+0x19a749)[0x563fa91a3749]
/lib64/libc.so.6(+0x3d8e0)[0x7f5f87e658e0]
/lib64/libc.so.6(+0x8927c)[0x7f5f87eb127c]
/lib64/libc.so.6(raise+0x12)[0x7f5f87e65842]
/lib64/libc.so.6(abort+0xcf)[0x7f5f87e5046b]
/usr/lib64/libglib-2.0.so.0(+0x1dddc)[0x7f5f895e6ddc]
/usr/lib64/libglib-2.0.so.0(g_assertion_message_expr+0x4b)[0x7f5f8964610b]
/usr/lib64/libglib-2.0.so.0(+0x52e86)[0x7f5f8961be86]
/home/tom/git/NOFORK/emacs/src/emacs(+0x2a7d80)[0x563fa92b0d80]
/home/tom/git/NOFORK/emacs/src/emacs(+0x25d6b4)[0x563fa92666b4]
/home/tom/git/NOFORK/emacs/src/emacs(+0x25f684)[0x563fa9268684]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20ba2b)[0x563fa9214a2b]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20c4de)[0x563fa92154de]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20b962)[0x563fa9214962]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20d76d)[0x563fa921676d]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20b962)[0x563fa9214962]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20c9d5)[0x563fa92159d5]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20ce07)[0x563fa9215e07]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20b866)[0x563fa9214866]
/home/tom/git/NOFORK/emacs/src/emacs(+0x20c9d5)[0x563fa92159d5]
/home/tom/git/NOFORK/emacs/src/emacs(+0x207b33)[0x563fa9210b33]
/home/tom/git/NOFORK/emacs/src/emacs(+0x285116)[0x563fa928e116]
/home/tom/git/NOFORK/emacs/src/emacs(+0x2063a7)[0x563fa920f3a7]
/home/tom/git/NOFORK/emacs/src/emacs(+0x28582f)[0x563fa928e82f]
/lib64/libc.so.6(+0x875a7)[0x7f5f87eaf5a7]
/lib64/libc.so.6(+0x10942c)[0x7f5f87f3142c]
Aborted
tom@host ~ $ ~/git/NOFORK/emacs/src/emacs -Q -batch -l ~/ni/sparc/prrequaestor.el -- --user-emacs-directory /tmp/lol2 --build-dir /tmp/test-build-dir --user-init-file ~/.emacs.d/prm-init.el --fun nif-scr --debug --specs ~/ni/sparc/sync-specs.el ^C
tom@host ~ $ ~/git/NOFORK/emacs/src/emacs -Q -batch -eval '(message "%S" system-configuration-features)'
"ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB"
tom@host ~ $ pushd git/NOFORK/emacs
~/git/NOFORK/emacs ~
tom@host ~/git/NOFORK/emacs $ git rev-parse HEAD
2e0c76e397811837fd119c1298a5606b4ef65be5
tom@host ~/git/NOFORK/emacs $