sync with Arch Linux ARM PKGBUILD, update to 20.0

I'm not sure if we have made any modifications to the PKGBUILD by Arch Linux ARM, but at a glance it looks like we just use it as is.

Arch Linux ARM updated to Kodi RPI 20 a little while ago, so this is just a sync with the Arch Linux ARM PKGBUILD to keep up to date.

Signed-off-by: Dan Johansen strit@manjaro.org