message: packages.md: document depends build targets
diff: @@ -181,3 +181,18 @@ For us, it's much easier to just link a static `libsecondary` into a shared
  static or dynamic `libseconday`, that's not our concern. With a static
  `libseconday`, when we need to link `libprimary` into our executable, there's no
  dependency chain to worry about as `libprimary` has all the symbols.
  +
  +## Build targets:
  +
  +To build an individual package (useful for debugging), following build targets are available.
  +
  + make ${package}
  + make ${package}_fetched
  + make ${package}_extracted
  + make ${package}_preprocessed
  + make ${package}_configured
  + make ${package}_built
  + make ${package}_staged
  + make ${package}_postprocessed
  + make ${package}_cached
  + make ${package}_cached_checksum
  