tools: return 77 if gtk_init() fails in the debug-gui

And when that happens, skip the tests because what's happening here is that
you're running tests as root, but your X server doesn't allow root to connect.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
24 jobs for master in 3 minutes and 29 seconds (queued for 2 seconds)
Status Job ID Name Coverage
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fedora:29@default-build

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fedora:30@build-no-debuggui-nodeps

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fedora:30@build-no-docs

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fedora:30@default-build

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  Deploy
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wayland-web

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