Fix various build and installation issues.
- Replace various Linuxisms in Makefile with little more portable code.
Remove now unnecessary build dependency of sysutils/coreutils.
- Install launcher wrappers with INSTALL_SCRIPT.
- Rename javaws launcher to itweb-javaws throughout. This conflicts with
a symlink created by java/javavmwrapper.
PR: ports/158826 
Reported by: glewis