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
Fix memory leak, reported by Coverity.

CID:		1229996