build: do not use link-zephyr

Use makefile targets to build and link final binary. This removes
dependency on a shell script which is not portable and imporves
dependency tracking when building.

Change-Id: Ib75f162cdb1dde35ccaf980658bfe70daaf581b6
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
2 files changed