Add [/usr]/lib/aarch64-linux-gnu/ to LD_LIBRARY_PATH

[sbernhard]

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[sbernhard]

Actually, the issue that neovim test was not successful was about this change in AppRun -> LD_LIBRARY_PATH.
I think, it make sense to use neovim instead of "hello" to run the test because hello is just to easy and doesn't has many dependencies. Therefore, we didn't saw this issue.

Can you please have a quick look at this @probonopd - and on #567 , too.