MFC r270650 (this is what should have been committed in r273497):

  Convert LIBCURSES to LIBNCURSES to fix "make checkdpadd"

  Also, add a missing LIBPANEL dependency for lldb

  Approved by: rpaulo (mentor)
  Suggested by: brooks
  Phabric: D675 (as part of a larger diff)
  PR: 192762
MFC r271365:

  Remove many false positives with make checkdpadd

  - Reduce DPADD and LDADD in checkdpadd to -l<foo>
  - Skip over -Wl,[es]*-group because -Wl,--end-group and
    -Wl,--start-group might be required to properly link objects (see
    usr.bin/clang/lldb as an example)

  This caveat has been present for a while with some components of
  the build. However, these false positives were made more more apparent
  after r269648.

  Phabric: D635
  Reviewed by: jmmv (an earlier version)
  PR: 192730
MFC r272055:

  Improve bsd.progs.mk compatibility with bsd.prog.mk

  1. Do not install FILES/SCRIPTS multiple times if PROGS is specified; this is
     already handled via bsd.prog.mk when it's called recursively (PR: 191055,
     191955).
  2. Some variables, like BINDIR and PROGNAME, default to a value if unset
     whereas others get appended to, like CFLAGS. Add support for the former case
     (PR: 191056)
  3. Make "checkdpadd" and "clean" available targets for recursive execution.

  Reviewed by: marcel, sjg
  Phabric: D822
  PR: 191055, 191056, 191955
  Sponsored by: EMC / Isilon Storage Division