example-ledflasher: convert to using cfgtree.mk

This change converts ledflasher to using the
cfgtree.mk-based product definition changes.

It depends on the cfgtree change and changes to
both crash_reporter and brillo_config to pull
in those two variables where expected.

This path may now be copied verbatim for out
of tree use.  The only missing convenience piece
is the envsetup.sh which a call to
  brunch product envsetup --generate
will fix.

TEST=full in-tree build in progress. an out of tree validating build will follow.

Change-Id: Iab912c4684a7e3a70c58431ae50c2a5c4f9bf953
9 files changed