To update in-tree Elftoolchain sources:

1.  Import upstream SVN revision 'NNNN' using:

    $ mkdir dist.new
    $ dist/tools/netbsd-base-system-import.sh -r NNNN -d dist.new \
          -m common -m libdwarf -m libelf

2.  "cvs import" the new directory using a vendor tag of 'FreeBSD'
    and a release-tag of 'elftoolchain-NNNN':

    $ cd dist.new
    $ cvs -d cvs.netbsd.org:/cvsroot import src/external/bsd/elftoolchain/dist \
          FreeBSD elftoolchain-NNNN

3.  Use the release tag used for the prior vendor import ('elftoolchain-PPPP'
    in the example below) to bring in the newly imported vendor branch changes
    into HEAD:

    $ cd ..
    $ cvs checkout -j elftoolchain-PPPP -j elftoolchain-NNNN dist