testing/avara: install files to /usr rather than /var

According to the FHS /var is meant for "variable data", a.k.a. files that change when the application is running and are created by the program. That's not what files installed by the package manager are. Instead such, architecture-independent, data files are supposed to be installed to /usr/share.

Ideally the binary gets installed to /usr/bin rather than /usr/share because it is architecture dependent, but it seems this game loads it resource files relative from where the binary is installed, thus moving it to /usr/bin doesn't work. So sadly we'll have to install this binary to /usr/share as well.