Graphviz: Restore support for per-target dependency graph options
The behaviors controlled by options `GRAPHVIZ_GENERATE_PER_TARGET` and
`GRAPHVIZ_GENERATE_DEPENDERS` were broken by commit 553658393c (Graphviz:
added test suite, fixes, enhancements, 2019-10-08, v3.17.0-rc1~615^2).
It had not been covered in the test suite previously, and those changes
left out checks for these features from the `default_options` case.
Implement the previously-existing behavior in the new graphviz
generation engine added by the above-mentioned commit.
Fixes: #20928
2 files changed
