af6e1a7e797995f introduces dependencies based in subpkgs,
but this makes "xbps-src show-build-deps" return cyclic
dependencies in some cases, i.e:
$ ./xbps-src show-build-deps kirigami2
cmake
extra-cmake-modules
kcoreaddons
kirigami2
qt5
$
This is because `kirigami2-devel` depends on `kirigami2`, thus
introducing a cycle.
Skip cycles completely, note that "show-build-deps" should not
be used to collect deps for cross compilation, because you can't
know what type of dependency it is: host or target.
a73783d17d