TODO: sbopkglint could complain if the SlackBuild sets SLKCFLAGS
      but there's no native code.

Future test ideas:

- duplicate files, maybe the error message could suggest a "ln -s" command
  to use if the file really does need to appear in multiple dirs.

- fonts. make sure they are what their filename says, and are installed to
  the correct /usr/share/fonts/* or /usr/share/kbd/consolefonts dir.

Other ideas:

When linting multiple packages, print a summary: 100 packages checked,
10 failed, 90 passed. Maybe with percentages too.

Clean up the output. Make it easier to grep.