app-misc/haguichi ebuild improvements

[Pinkbyte]

Fix sandbox violations, rework whole ebuild to use cmake-utils and vala eclasses

[mradermaxlol]

@Pinkbyte isn't it better to use
export VALAC="$(type -p valac-$(vala_best_api_version))" ?

[Pinkbyte]

If you look into vala.eclass, you will see, that VALAC environment variable is already exported in vala_src_prepare

Unfortunately FindVala.cmake in this package completely ignores it. If you can patch buildsystem to make it consider this variable - feel free to do so ;-)

[mradermaxlol]

@Pinkbyte hmm, that's damn bad. I'll take a look at Budgie/other Vala projects' configs and will try to commit changes upstream ;)

I'm then accepting the PR, thanks a lot! Gotta update the ebuilds to EAPI 6 now :)