Mark as unsupported unless CONFIG_FEATURE_TAR_EXCLUDE is defined.

testsuite/tar/tar-handles-empty-include-and-non-empty-exclude-list

@@ -1,3 +1,4 @@
+# UNSUPPORTED: CONFIG_FEATURE_TAR_EXCLUDE
 touch foo
 tar cf foo.tar foo
 echo foo >foo.exclude

testsuite/tar/tar-handles-exclude-and-extract-lists

@@ -1,3 +1,4 @@
+# UNSUPPORTED: CONFIG_FEATURE_TAR_EXCLUDE
 touch foo bar baz
 tar cf foo.tar foo bar baz
 echo foo >foo.exclude

testsuite/tar/tar-handles-nested-exclude

@@ -1,3 +1,4 @@
+# UNSUPPORTED: CONFIG_FEATURE_TAR_EXCLUDE
 mkdir foo
 touch foo/bar
 tar cf foo.tar foo