tests: skip ls/stat-free-color on XFS, rather than always failing

* tests/init.cfg (require_dirent_d_type_): Manually skip when
"." is an xfs file system.

tests/init.cfg

@@ -362,6 +362,12 @@ require_dirent_d_type_()
   python < /dev/null \
     || skip_ python missing: assuming no d_type support
 
+  # Manually exclude xfs, since the test would mistakenly report
+  # that it has d_type support: d_type == DT_DIR for "." and "..",
+  # but DT_UNKNOWN for all other types.
+  df -x xfs . > /dev/null 2>&1 \
+    || skip_ requires d_type support
+
   python $abs_srcdir/d_type-check \
     || skip_ requires d_type support
 }