- Fails to build on macOS, due to not finding features.h header.
  For now, it's commented-out via a patch until there's a better
  solution.

- We should probably use the system's elf.h, if possible.

- The author doesn't seem to use any licenses. However, he does
  have some GPL'd stuff in his repo, like elf.h for example.

  So for now we'll add GPL3 to LICENSE, and perhaps can nuke this
  TODO item at a later when we're certain we have it right.

- elfhash's Makefile hard-codes gcc and CFLAGS, and as such, doesn't
  honor the $(CC) and $(CFLAGS) variables passed by pkgsrc.
