Using the cross-page links, we can generate a directed graph showing the
topology of which pages refer to other pages. This is not just for fun:
the links show how often a page is linked (since links are not
deduplicated on purpose), which pairs of pages only have links in one
direction (where a link in the other direction may be useful), which
groups of closely-interlinked pages exist, and which pages have few or
no links to other pages.
The EXTRA_MARKDOWN_CHECK_ARGS argument to the check-markdown script can
be used to inject the -g flag for generating the graph on all manpages.
On macOS, CMake incorrectly tries to add and/or remove rpaths from files
that it has already processed when it performs installation. Setting the
rpaths during the build process ensures that they are only set once, and
as a bonus, makes installation slightly more performant.
Fixes#10055.
We use the environment variable SERENITY_SOURCE_DIR to resolve and check
icon links. This is a bit inconvenient as SERENITY_SOURCE_DIR needs to
be set correctly before invoking the markdown checker, but as we use it
through the check-markdown script anyways, I think it's not a problem.
