... when gzip is selected but not gunzip nor zcat, or when bzip2 is
selected but not bunzip2 nor bzcat.
This regression is introduced in b130f9f758b6404c6d0911a1c120937ae6ab47f8
("Allow 'gzip -d' and 'bzip2 -d' without gunzip or bunzip2")
Signed-off-by: Kang-Che Sung <explorer09@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>