Isolate code better for unused options, config option to enable long
options, add some conditions to the tar tests in testsuite.
diff --git a/testsuite/tar/tar-handles-multiple-X-options b/testsuite/tar/tar-handles-multiple-X-options
index 8321af8..155b27e 100644
--- a/testsuite/tar/tar-handles-multiple-X-options
+++ b/testsuite/tar/tar-handles-multiple-X-options
@@ -1,3 +1,5 @@
+# FEATURE: CONFIG_FEATURE_TAR_FROM
+# FEATURE: CONFIG_FEATURE_TAR_CREATE
 touch foo
 touch bar
 tar cf foo.tar foo bar