xfs_scrub: report optional features in version string

xfs_scrub: report optional features in version string

Ted T'so reported brittleness in the fstests logic in generic/45[34] to
detect whether or not xfs_scrub is capable of detecting Unicode mischief
in directory and xattr names.  This is a compile-time feature, since we
do not assume that all distros will want to ship xfsprogs with libicu.

Rather than relying on ldd tests (which don't work at all if xfs_scrub
is compiled statically), let's have -V print whether or not the feature
is built into the tool.  Phase 5 still requires the presence of "UTF-8"
in LC_MESSAGES to enable Unicode confusable detection; this merely makes
the feature easier to discover.

Reported-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>