Update ebuild to support gentoo profile 17.1
Gentoo updated to profile 17.1, which changed where the python plugins are located. The attached ebuild update (specifically, the "cura-lulzbot-17.1.libfix.patch") is currently a bit of a kludge (I'm not a python dev), but fixes the plugin search path to look in the correct location for 64-bit architectures. Also fixed the generate_version python script to support 3.6.x, and updated to reference the new gitlab repo URI vs the old (and offline) alephobjects repo URI.
In addition, attaching an ebuild to support building the 3.6.21 release version.cura-lulzbot-3.6.21.ebuild