A lot of autoconf-based scripts expect --with-foo-dir=$(STAGING_DIR)/usr
and break if they can't find bin/foo-config as a child of that path.

Putting things in $(STAGING_DIR)/host/bin seems to be suboptimal; I
could change the install path but there's no saying what that would
break.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>