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 after: 2 weeks


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271365 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f