Header-only vs. compiled libraries, library compilation selection

I'm think we're missing a mention of "header only vs. compiled libraries" in the discussion part (maybe in the introduction or the getting started, without having to scan through all of `user-guide/header-organization-compilation.html`.

We're also missing how to use `--with-`, which can alleviate compile times if you're not using all libraries.

Start with user-guide/header-organization-compilation.html and inspect the discussion, introduction, or getting-started documentation mentioned in the issue. Add an accessible explanation of header-only versus compiled libraries and document how --with- can reduce compile times when unused libraries are excluded. Done means both topics are covered without requiring readers to scan the detailed user guide.

Written by the indexing model from the issue text.