net-p2p/jackett: improve port Makefile

Made some changes to Makefile to more closely follow the Porter's
handbook, namely:

• specify a file the port depends on instead of a package name in RUN_DEPENDS
• use COPYTREE_SHARE for copying directory contents to the staging area

PR: 287951
Reported by: arrowd
Approved by: Ralf van der Enden <tremere@cainites.net> (maintainer)