How to install AUR package in home directory?

IntelliJ IDEA Ultimate is not available as an Arch Linux core package, and has a built-in upgrade mechanism. For these reasons it would be convenient to install it into my home directory, letting it upgrade itself without needing to rebuild the AUR package or running anything as root. Is this possible? As far as I can tell from the PKGBUILD it refers to a pkgdir variable, but I can't find any makepkg flags to control it and export pkgdir="${HOME}/bin" doesn't seem to help.