[buildsystem] posix: add legacy xbmc links for libdir, includedir and datarootdir

fixes legacy xbmc binary addons, e.g. pvr
Merge pull request #5567 from wsnipex/legacy

[buildsystem] posix: add legacy xbmc links for libdir, includedir and da...
fixed: Asserting on empty protocol is too extreme, it also fails with file://...
Merge pull request #5574 from arnova/posix_file_fix

fixed: Asserting on empty protocol is too extreme