graphics/darktable: various build fixes for 3.6.0
- add missing LIB_DEPENDS on print/harfbuzz and devel/icu, found missing by: make stage-qa
- make pkg-plist complete, misses some files, found missing by: make check-plist
- disable LTO option for now (OPTIONS_EXCLUDE=LTO), since the workaround for cmake 3.21 regressions around static libraries (which darktable uses) is USES=cmake:noninja - but the RawSpeed library embedded into darktable requires ninja for LTO builds.
Approved by: Jean-Sébastien Pédron (dumbbell@, maintainer)