[PATCH] common/rc: fix _check_xfs_scrub_does_unicode on newer versions of libc-bin

["Theodore Ts'o" <tytso@mit.edu>]

Debian 10 uses ldd from glibc 2.28, where as Debian 11 uses ldd from
glibc 2.31.  Sometime between glibc 2.28 and 2.31, ldd has been
changed so that the message "not a dynamic executable" is sent stderr,
where before it was sent to stdout.  As a result, it caused
regressions for tests such as generic/453 which uses
_check_xfs_scurb_does_unicode:

generic/453 5s ... 	[22:42:03] [22:42:08]- output mismatch (see /results/xfs/results-4k/generic/453.out.bad)
    --- tests/generic/453.out	2022-01-08 15:15:15.000000000 -0500
    +++ /results/xfs/results-4k/generic/453.out.bad	2022-01-08 22:42:08.596982251 -0500
    @@ -4,3 +4,4 @@
     Test files
     Uniqueness of inodes?
     Test XFS online scrub, if applicable
    +	not a dynamic executable
    ...

Fix this by sending stderr from ldd to /dev/null.  This is not a
perfect solution, since it means that even if xfs_scrub was compiled
with libicui18n, we will skip the online scrub portion of generic/453.
However, this fixes the regression when runtime OS is changed from
Debian Buster to Debian Bullseye when xfsprogs is built statically.

In the long run, it would be nice if we could determine whether
xfs_scrub has unicode support without using ldd --- perhaps by
signally this in the output of xfs_scrub -V --- but we'll need to
discuss this with the xfsprogs maintainers.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 common/rc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/rc b/common/rc
index 87b9b69b..add6170c 100644
--- a/common/rc
+++ b/common/rc
@@ -4909,7 +4909,7 @@ _check_xfs_scrub_does_unicode() {
 
 	# We only care if xfs_scrub has unicode string support...
 	if ! type ldd > /dev/null 2>&1 || \
-	   ! ldd "${XFS_SCRUB_PROG}" | grep -q libicui18n; then
+	   ! ldd "${XFS_SCRUB_PROG}" 2> /dev/null | grep -q libicui18n; then
 		return 1
 	fi
 
-- 
2.31.0