[buildarmpkg] we should install packages after building into chroot
Especially for batch building we might need a feature to install the package after building it. This can be done by using the following cmd line:
$NSPAWN $BUILDDIR/$ARCH/ --chdir=/build/ makepkg -Asci --noconfirm
... Question is: do we want to install it by default or add another switch to buildarmpkg?