From: Laurent Vivier <lvivier@redhat.com>

The passt networking backend uses functions from the GIO library,
such as g_subprocess_launcher_new(), to manage its daemon process.
So, building with passt enabled requires GIO to be available.

If we enable passt and disable gio the build fails during linkage with
undefined reference errors:

  /usr/bin/ld: libsystem.a.p/net_passt.c.o: in function `net_passt_start_daemon':
  net/passt.c:250: undefined reference to `g_subprocess_launcher_new'
  /usr/bin/ld: net/passt.c:251: undefined reference to `g_subprocess_launcher_take_fd'
  /usr/bin/ld: net/passt.c:253: undefined reference to `g_subprocess_launcher_spawnv'
  /usr/bin/ld: net/passt.c:256: undefined reference to `g_object_unref'
  /usr/bin/ld: net/passt.c:263: undefined reference to `g_subprocess_wait'
  /usr/bin/ld: net/passt.c:268: undefined reference to `g_subprocess_get_if_exited'
  /usr/bin/ld: libsystem.a.p/net_passt.c.o: in function `glib_autoptr_clear_GSubprocess':
  /usr/include/glib-2.0/gio/gio-autocleanups.h:132: undefined reference to `g_object_unref'
  /usr/bin/ld: libsystem.a.p/net_passt.c.o: in function `net_passt_start_daemon':
  net/passt.c:269: undefined reference to `g_subprocess_get_exit_status'

Fix this by adding an explicit weson dependency on GIO for the passt
option.
The existing dependency on linux is kept because passt is only available
on this OS.

Cc: qemu-stable@nongnu.org
Fixes: 854ee02b222 ("net: Add passt network backend")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3121
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
(cherry picked from commit 4ccca2cc05a2d904d1e25365accf3bcbe553c8b0)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/meson.build b/meson.build
index 50c774a195..b7db736bbf 100644
--- a/meson.build
+++ b/meson.build
@@ -1287,6 +1287,7 @@ endif
 
 enable_passt = get_option('passt') \
   .require(host_os == 'linux', error_message: 'passt is supported only on Linux') \
+  .require(gio.found(), error_message: 'passt requires gio') \
   .allowed()
 
 vde = not_found
-- 
2.47.3