If I create a project with kiln new and add a broken symlink to it:

$ tree
.
├── config.toml
├── content
│   └── _index.gmi
├── public
│   ├── atom.xml
│   └── index.gmi
├── static
│   └── no-such-file -> ../no-such-file
└── templates
    └── _default
        ├── atom.xml
        ├── index.gmi
        └── page.gmi

5 directories, 8 files

... and then run kiln build, the error raised from trying to access the broken symlink is reported as the entire static dir missing:

$ kiln build
2022/09/24 12:22:36 static_dir 'static' does not exist