packaging: build: simplify plain files installation

copy packaging directory recursive excluded generated and other files.
no need to explicitly specify each file at makefile.

this should ease maintenance and reduce future commit size and conflicts.

Change-Id: I294a14f7e954ec05ef497e870f9937e68b2a2bbc
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>