When user installed a new version of ST (or just a different derivation),
GNOME Shell would lose the association of the windows with the icon.
Since the package needs to be installed in order for the desktop file
to be available, having the path absolute is useless any way.
Running `update-source-version` with `--system` flag passes it
to `nix-build -A $attr.src`, which requires that an appropriate
builders are set on the system.
It works for me because I have aarch64-linux builder configured
but it is broken for other users and r-ryantm.
https://www.sublimetext.com/download
* works with my 7 year old license so far
* i686 is no longer supported
* aarch64 support has been added
* adds harware accelerated (needs libGL.so.1)
* adds python 3.8 plugin host (needs libssl.so and libcrypto.so)
