[libgudev/wip/hadess/use-constant-test] tests: Use "skip" constant we just added

[Bastien Nocera <hadess src gnome org>]

commit f6ec5ecb6ef68272392a7e950b3f60194c42f1ee
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Sep 7 17:19:05 2021 +0200

    tests: Use "skip" constant we just added
    
    Spotted by Mike Gilbert:
    https://gitlab.gnome.org/GNOME/libgudev/-/merge_requests/20#note_1265114

 tests/test-double.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/tests/test-double.c b/tests/test-double.c
index c518e7a..886fa02 100644
--- a/tests/test-double.c
+++ b/tests/test-double.c
@@ -59,7 +59,7 @@ int main(int argc, char **argv)
 
        /* Skip if locale is unavailable */
        if (setlocale (LC_NUMERIC, "fr_FR.UTF-8") == NULL)
-               return 77;
+               return GNU_SKIP_RETURNCODE;
 
        g_test_init (&argc, &argv, NULL);