sync PKGBUILD from Arch, update to 20.0
I'm not sure if we have made any modifications to the PKGBUILD by Arch, but at a glance it looks like we just use it as is.
Arch updated to Kodi 20 a little while ago, so this is just a sync with the Arch PKGBUILD to keep up to date.
Signed-off-by: Dan Johansen strit@manjaro.org