Log Message:
Move -larchive from the general LIBS variable to each program that needs it,
prevents us from attempting to link the inplace libarchive against itself.
Fixes build on systems which do not include a native libarchive, and avoids
possible issues on systems which do.

Tested on SmartOS (no native libarchive) and OS X in both builtin and pkgsrc
configurations.  Ok joerg@.